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Abstract:

A tubular combustion chamber including a tubular combustion chamber whose
front-end is open; and, fuel-gas spraying nozzles and
oxygen-containing-gas spraying nozzles, for spraying a fuel and an
oxygen-containing-gas separately and individually, or for spraying a
premixed gas; wherein respective orifices of the respective nozzles face
toward an inner surface of the combustion chamber, so as to spray the
fuel-gas and the oxygen-containing-gas in a neighborhood of a tangential
direction of an inner circumferential wall of the. combustion chamber;
wherein the tubular flame burner is a multi-stage tubular burner that is
unified in a body, by using a plurality of the tubular flame burners, and
by connecting the front-end of the tubular flame burner with a smaller
inner diameter of the combustion chamber into the rear-end of the tubular
flame burner with a greater inner diameter of the combustion chamber.

Claims:

1. A tubular flame burner comprising:a tubular combustion chamber whose
front-end is open; and,fuel-gas spraying nozzles and
oxygen-containing-gas spraying nozzles, for spraying a fuel and an
oxygen-containing-gas separately and individually, or for spraying a
premixed gas; wherein respective orifices of the respective nozzles face
toward an inner surface of the combustion chamber, so as to spray the
fuel-gas and the oxygen-containing-gas in a neighborhood of a tangential
direction of an inner circumferential wall of the combustion
chamber;wherein the tubular flame burner is a multi-stage tubular burner
that is unified in a body, by using a plurality of the tubular flame
burners, and by connecting the front-end of the tubular flame burner with
a smaller inner diameter of the combustion chamber into the rear-end of
the tubular flame burner with a greater inner diameter of the combustion
chamber.

2. A method for controlling combustion by a tubular flame burner
comprising:a step for preparing a tubular combustion chamber whose
front-end is open, wherein respective nozzle orifices of the nozzles face
an inner wall of the combustion chamber for separately spraying fuel and
an oxygen-containing-gas, or spraying a premixed gas as the fuel and the
oxygen-containing-gas;a step for preparing a multi-stage tubular flame
burner comprising a plurality of tubular flame burners, by unifying the
plurality of tubular flame burners to become one body, wherein respective
spaying directions of the respective nozzles are in a neighborhood of a
tangential direction of an inner circumferential wall of the combustion
chamber, and wherein a front-end of the tubular flame burner with a
smaller inner diameter of the combustion chamber is connected into a
rear-end of the tubular flame burner with a greater inner diameter of the
combustion chamber; and,a step for controlling combustion by selecting a
tubular flame burner to be used from the plurality of tubular flame
burners that form the multi-stage tubular flame burner, in accordance
with the combustion load.

Description:

[0001]This application is a Divisional application of application Ser. No.
10/514,668 filed Jan. 4, 2005, which is the United States national phase
application of International application PCT/JP2003/010059 filed Aug. 7,
2003. The entire contents of each of application Ser. No. 10/514,668 and
International application PCT/JP2003/010059 are incorporated by reference
herein.

TECHNICAL FIELD

[0002]The present invention relates to a burner included in a furnace or a
combustion chamber. The present invention relates to a combustion burner
included and used in an industrial furnace or a combustion chamber.

BACKGROUND OF THE INVENTION

[0003]In general, an industrial-use gas burner has been known such as a
configuration whose flame is formed in front of the tip of a burner.
Concerning such a burner, fuel supplied through a fuel-passage and
combustion air supplied through an air-passage are sprayed in front of
the burner from the nozzle, resulting in forming the turbulence by the
sprayed air and fuel.

[0004]Accordingly, the combustion flame becomes turbulent, and the partial
flame extinction happens. Such partial flame extinction makes the
combustion not stable. In order to avoid such a phenomenon as much as
possible, nozzle is designed to exhibit the optimal nozzle-flow-velocity
so that stable combustion is obtained, which corresponds to the
particular heating value and combustion speed of the employed fuel from
the thermal perspective and the perspective of fluid dynamics.

[0005]In such a case, the stable combustion is done when using the fuel
suitable for the designed nozzle. On the other hand, combustion becomes
unstable when using other kinds of fuel.

[0006]Furthermore, combustion reaction is always performed within a flame
that has a certain volume, so the reaction is required to continue for a
long period. In such a case, NOx or soot is apt to generate by the reason
of the long combustion time. And, the flame has a partial
high-temperature region and a low-temperature region, wherein NOx is easy
to generate in the high-temperature region, and soot is easy to generate
in the low-temperature region.

[0007]On the other hand, a tubular flame burner is disclosed in Japanese
Unexamined Patent Application Publication No. 11-281015. This publication
includes a tubular combustion chamber of which one-end opens and a nozzle
for spraying a fuel gas and a nozzle for spraying an
oxygen-containing-gas in the neighborhood of the closed end thereof.
Here, the nozzle is located, facing in the tangential direction of the
inner circumferential wall of the aforementioned combustion chamber.

[0008]With the aforementioned tubular flame burner, stable flame is formed
in a high-speed swirl within the burner, accordingly combustion is
performed with small irregularities in the temperature of a combustion
flame. Therefore, no partial high-temperature regions are easy to be
formed. Furthermore, stable combustion is achieved even with a low oxygen
ratio or air excess ratio. Consequently, the tubular flame burner has the
advantage to reduce harmful substances such as NOx or the like, unburned
portions of hydrocarbon or the like, and environmental pollutants such as
soot and the like, as well as to reduce of the size thereof.

[0009]FIG. 8 is explanatory diagrams which show an conventional tubular
flame burner, wherein FIG. 8A is a configuration diagram which shows the
tubular flame burner, and FIG. 8B is a cross-sectional view taken along
line B-B in FIG. 8A. The tubular flame burner includes a tubular
combustion chamber 121, whose one end opens for serving as an exhaust
vent for an exhaust gas. Furthermore, the tubular flame burner includes
long slits on the other end along the tube axis, each of which are
connected to one of nozzles 122 for separately supplying a fuel gas and a
nozzle for supplying an oxygen-containing-gas.

[0010]The nozzles 122 are disposed in a tangential direction of the inner
wall of the combustion chamber 121 for spraying the fuel gas and the
oxygen-containing-gas so as to form a swirl thereof within the combustion
chamber 121. Furthermore, the tip of each nozzle 122 is formed flat with
a reduced orifice for spraying the fuel gas and the oxygen-containing-gas
at high speed. Note that reference numeral 123 denotes a spark plug.

[0011]In the above-mentioned burner having such a configuration, when a
mixture gas is ignited, which forms a swirl (such a swirl is generated by
the fuel gas and the oxygen-containing-gas sprayed from the nozzles 122),
the gas within the combustion chamber 121 is stratified into concentric
gas layers with different densities, due to difference in the density of
the gas and the centrifugal force. That is to say, a high-temperature and
low-density exhaust gas exists close to the axis of the combustion
chamber 121, and a high-density unburned gas exists close to the inner
wall of the combustion chamber 121 (away from the axis thereof). This
state exhibits remarkable stability from the viewpoint of fluid dynamics.
In this case, a tube-shaped flame is formed, and the gas flow is
stratified into stable layers, thereby forming a film-shaped stable
flame. The position of the flame is determined, being influenced by the
position, wherein two factors (one is the exhaust gas speed toward the
center of the combustion chamber 121 and the other is the flame
propagation speed) balance each other in natural process. In FIG. 8A,
reference numeral 124 denotes a tube-shaped flame.

[0012]Furthermore, an unburned low-temperature gas forms a boundary layer
near the inner wall of the combustion chamber. Accordingly, the wall of
the combustion chamber 121 is not heated by the direct heat transfer to a
degree of a high temperature, resulting in avoiding the thermal loss,
which means, preventing the heat from releasing to the outside of the
wall. That is to say, the aforementioned burner has the effective
advantage on great thermal insulation, thereby maintaining thermal
stability of combustion.

[0013]The gas within the combustion chamber 121 flows downstream while
swirling, and at the same time, the mixture gas around the inner wall
continuously burns so as to form a tubular flame. And, a generated
exhaust gas flows toward the axis of the combustion chamber 121 so as to
be discharged from the open-end.

[0014]However, the conventional tubular flame burner having such a
configuration happens to have problems as follows. That is to say:

[0015]In general, a fuel gas that has a small heating value invites a
disadvantage, that is, the range of the air excess ratio is extremely
narrow, taking into consideration the usable range for igniting by
electronic spark. Therefore, it is extremely difficult to ignite such a
fuel without premixing of the fuel gas and the oxygen-containing-gas.

[0016]The aforementioned tubular flame burner has the same difficult
problem on igniting by the electronic spark due to the limited range of
the air excess ratio of the fuel gas and the oxygen-containing-gas
suitable for the ignition. Accordingly, it may be a case, the
aforementioned tubular flame burner requires a pilot burner.

[0017]Furthermore, the conventional tubular flame burner has such problems
as the following description.

(1) In particular, in case of using oil fuel or heavy-hydrocarbon fuel
such as a propane gas, the free carbon content within the fuel emits
light during combustion, resulting in forming a luminous flame. The
luminous flame has such a characteristic that the radiation rate is high
by himself, resulting in increasing radiation heat from the luminous
flame. Accordingly, when the burner having a configuration, whose
luminous flame is located in the position capable of viewing from the
heated material, the aforementioned burner exhibits high heat transfer
efficiency. However, with the aforementioned conventional burner, the
fuel sprayed into the furnace does not form a luminous flame, but forms a
transparent exhaust gas that has small emissivity due to the complete
combustion of the fuel within the combustion chamber. This leads to small
heat transfer efficiency of the combustion method with the conventional
tubular burner.(2) With the conventional tubular burner, no soot is
generated due to complete combustion of the fuel. Accordingly, the
conventional tubular burner is not used in case of requiring soot, for
example, such as carburizing steel with high efficiency, for example.(3)
The conventional tubular burner exhibits excellent combustion performance
due to complete combustion of the fuel within the combustion chamber, but
NOx is easy to be generated.

[0018]Furthermore, the conventional tubular flame burner has a
configuration, wherein, in order to form a tubular flame, the respective
supply nozzles that are flat along the tube axis are connected to the
slits extending along the tube axis. (The slits are located in the
tubular combustion chamber.) The conventional tubular flame burner is
used while spraying the fuel gas and the oxygen-containing-gas into the
combustion chamber, simultaneously with forming high-speed swirl of the
sprayed fuel gas and the oxygen-containing-gas. Accordingly, the
conventional tubular flame burner causes such a problem that relatively
high pressure loss happens at the slits. That is to say, in general, the
fuel gas and the oxygen-containing-gas are supplied with a constant
pressure. Accordingly, there is need to increase the flow of the fuel gas
and the oxygen-containing-gas, in case of increasing the combustion load.
But in this case, the pressure loss at the slits increases, proportional
to the squire value of the flow speed, ending up in a small increase in a
combustion load.

[0019]Contrarily, when the conventional tubular flame burner having a
configuration is used (wherein each slit is formed with an increased
cross-sectional area so as to reduce the pressure loss at the slit), the
flow speed of the fuel gas and the oxygen-containing-gas remarkably
reduce along the tangential direction of the inner wall of the combustion
chamber. Such reduction happens in the event that combustion is performed
with a small flow of the fuel gas and the oxygen-containing-gas
corresponding to a small combustion load. Accordingly, a tube-shaped
flame is not formed, leading to such a problem as increased amount of
NOx, soot, and the like, generated in the combustion chamber.

[0020]As described above, concerning the conventional tubular flame
burner, the problem is as follows. In the event that the supply flow of
the fuel gas and the oxygen-containing-gas is adjusted corresponding to
the change in the combustion load, it may be a case, the flow speed of
the fuel gas and the oxygen-containing-gas is out of the range of the
suitable flow speed. The suitable flow speed is determined between the
flame formation minimal flow speed required for formation of a
tube-shaped flame and the permissive maximal flow speed dependent upon
the pressure loss, inviting difficulty in stable combustion in a wide
range of the combustion load, and resulting in a narrow range of the
combustion load suitable for the conventional tubular flame burner.

[0021]Furthermore, there is need to further improve the aforementioned
conventional tubular flame burner in order to employ fuel with lower heat
output so as to improve the practical use.

[0022]Accordingly, the present invention has been conceived in order to
solve the aforementioned problems of the conventional tubular flame
burner. And the present invention has been conceived and studied in order
to provide a tubular flame burner having a new flame formation mechanism,
wherein various kinds of fuel can be used, wherein combustion is
performed in a wide combustion range, and wherein stable combustion is
maintained even with a wide range of the change in combustion load. And
in the present invention, stable combustion can be performed, and
discharge of an environmental pollution substance created due to
combustion is prevented.

SUMMARY OF THE INVENTION

[0023]The present invention comprises the following devices and methods in
order to solve the above-described conventional problems. That is to say:

[0024]Firstly, a tubular flame burner comprises:

[0025]a tubular combustion chamber having two ends of an open end and a
closed end including an ignition device; and

[0026]fuel-gas spraying nozzles and oxygen-containing-gas spraying
nozzles, each orifice of which faces toward the inner face of the
combustion chamber so as to spray a fuel gas and an oxygen-containing-gas
in a neighborhood of a tangential direction of the inner circumferential
wall of the combustion chamber;

[0027]wherein the ignition device is disposed at a position between
[0028]a point of the tube axis extending along the longitudinal direction
of the combustion chamber, and [0029]a point of an axis away from the
tube axis along the cross-sectional direction orthogonal to the
longitudinal direction thereof by 1/2 of the radius thereof.

[0030]Secondly, a tubular flame burner comprises:

[0031]a tubular combustion chamber wherein the front-end opens; and

[0032]fuel-gas spraying nozzles and oxygen-containing-gas spraying
nozzles, each orifice of which faces toward the inner face of the
combustion chamber so as to spray a gas in a neighborhood of a tangential
direction of the inner circumferential wall of the combustion chamber,

[0033]wherein a tube as a component of the combustion chamber, wherein the
fuel and the oxygen-containing-gas are discharged from the nozzle
orifices of the combustion chamber, is formed of an inner tube and an
outer tube for adjusting the length of the combustion chamber by sliding
the outer inner face along the outer face of the inner tube.

[0034]Thirdly, a tubular flame burner comprises:

[0035]a tubular combustion chamber wherein the front-end opens; and

[0036]fuel-gas spraying nozzles and oxygen-containing-gas spraying
nozzles, each orifice of which faces toward the inner face of the
combustion chamber, which can spray gas in a neighborhood of a tangential
direction of the inner circumferential wall of the combustion chamber,
for separately spraying fuel and an oxygen-containing-gas, or spraying a
premixed gas,

[0037]wherein the tubular flame burner is formed of a plurality of the
tubular flame burners,

[0038]and wherein the tubular flame burner is a multi-stage tubular flame
burner having a configuration, wherein the rear-end of the tubular flame
burner with a greater inner diameter of the combustion chamber is
connected to the front-end of the tubular flame burner with a smaller
inner diameter of the combustion chamber. In such a way, the multi-stage
tubular flame burner is formed.

[0039]Fourthly, a tubular flame burner comprises:

[0040]a tubular combustion chamber wherein the front-end opens;

[0041]fuel-gas spraying nozzles and oxygen-containing-gas spraying
nozzles, each orifice of which faces toward the inner face of the
combustion chamber, which can spray gas in a neighborhood of a tangential
direction of the inner circumferential wall of the combustion chamber;
and

[0042]an outer tube with a longer inner diameter than the outer diameter
of the combustion chamber, which covers the combustion chamber;

[0043]wherein a gap between the outer face of the combustion chamber and
the inner face of the outer tube provides a passage for a fuel gas or an
oxygen-containing-gas to pass before supplying these gases to the
spraying nozzles.

[0044]Fifthly, a combustion controller for a tubular flame burner
comprises:

[0045]a tubular combustion chamber wherein the front-end opens;

[0046]a plurality of fuel-gas spraying nozzles and a plurality of
oxygen-containing-gas spraying nozzles, each orifice of which faces
toward the inner face of the combustion chamber, for spraying generally
toward a tangential direction of the inner circumferential wall of the
combustion chamber. Here, these nozzles are disposed along at least one
direction of the longitudinal direction and the circumferential
direction;

[0047]switching valves disposed on supply lines, wherein each of the
switching valves are connected to the corresponding one of the nozzles
included in the tubular flame burner; and

[0048]means for controlling on/off of the switching valves so that the
spraying speed from the nozzles is maintained in a predetermined range
corresponding to the combustion load applied to the tubular flame burner.

[0049]Sixthly, a combustion controller for a tubular flame burner
comprises:

[0050]a tubular flame burner comprising: [0051]a tubular combustion
chamber, wherein the front-end opens; and [0052]a plurality of nozzles,
each orifice of which faces toward the inner face of the combustion
chamber, for spraying a premixed gas formed of a fuel gas and an
oxygen-containing-gas in a neighborhood of a tangential direction of the
inner circumferential wall of the combustion chamber. Here, these nozzles
are disposed along at least one direction of the longitudinal direction
and the circumferential direction;

[0053]switching valves disposed on supply lines each of which are
connected to the corresponding one of the nozzles; and

[0054]control means for controlling on/off of the switching valves so that
the spraying speed from the nozzles is maintained in a predetermined
range corresponding to the combustion load applied to the tubular flame
burner.

[0055]Seventhly, a combustion controller for a tubular flame burner
comprises:

[0056]a tubular flame burner comprising: [0057]a tubular combustion
chamber, wherein the front-end opens; and [0058]a plurality of fuel-gas
spraying nozzles and a plurality of oxygen-containing-gas spraying
nozzles, each orifice of which faces toward the inner face of the
combustion chamber, for spraying in a neighborhood of a tangential
direction of the inner circumferential wall of the combustion chamber;
[0059]switching valves disposed on supply lines, wherein the respective
switching valves are connected to the corresponding one of the nozzles
included in the tubular flame burner; [0060]control means for controlling
on/off of the switching valves so that the spraying speed from the
nozzles is maintained in a predetermined range corresponding to the
combustion load applied to the tubular flame burner; [0061]adjusting
means for adjusting the aperture area of each nozzle orifice to be
variable; and [0062]control means for adjusting the aperture area of each
nozzle orifice to be variable by controlling the adjusting means so that
the spraying speed from the nozzles is maintained in a predetermined
range corresponding to the combustion load applied to the tubular flame
burner. [0063]Eighthly, a combustion controller for a tubular flame
burner comprises:

[0064]a tubular flame burner comprising: [0065]a tubular combustion
chamber wherein the front-end opens; and [0066]a plurality of fuel-gas
spraying nozzles and a plurality of oxygen-containing-gas spraying
nozzles, wherein each orifice of the nozzle faces toward the inner face
of the combustion chamber, for spraying a premixed gas formed of a fuel
gas and an oxygen-containing-gas in a neighborhood of a tangential
direction of the inner circumferential wall of the combustion chamber;

[0067]switching valves disposed on supply lines, wherein each of the
switching valves are connected to the corresponding one of the nozzles
included in the tubular flame burner;

[0068]control means for controlling on/off of the switching valves so that
the spraying speed from the nozzles is maintained in a predetermined
range corresponding to the combustion load applied to the tubular flame
burner;

[0069]adjusting means for adjusting the aperture area of each nozzle
orifice to be variable; and

[0070]control means for adjusting the aperture area of each nozzle orifice
to be variable by controlling the adjusting means so that the spraying
speed from the nozzles is maintained in a predetermined range
corresponding to the combustion load applied to the tubular flame burner.

[0071]Ninthly, a combustion control method for a tubular flame burner
comprises:

[0072]a step for preparing a tubular combustion chamber, wherein the
front-end opens, and a plurality of fuel-spraying nozzles and a plurality
of oxygen-containing-gas spraying nozzles. Here, each nozzle orifice
faces the inner wall of the combustion chamber, disposed along at least
one direction of the longitudinal direction and the circumferential
direction;

[0073]a step for connecting supply lines to the nozzles, and providing
switching valves to the supply lines;

[0074]a step for adjusting the fuel-spraying nozzles and the
oxygen-containing-gas spraying nozzles so that each spraying direction is
in a neighborhood of a tangential direction of the inner circumferential
wall of the combustion chamber, to control combustion; and

[0075]a step for controlling on/off of the switching valves so that the
spraying speed from the nozzles is maintained in a predetermined range
corresponding to the combustion load applied to the tubular flame burner.

[0076]Tenthly, a method for controlling a combustion by a tubular flame
burner comprising:

[0077]a step for preparing a tubular combustion chamber wherein the
front-end opens, and for preparing a plurality of nozzles, wherein each
nozzle orifice faces the inner wall of the combustion chamber, for
spraying a premixed gas formed of a fuel gas and an oxygen-containing-gas
and wherein each nozzle orifice is disposed along at least one direction
of the longitudinal direction and the circumferential direction;

[0078]a step for connecting supply lines to the nozzles, and providing
switching valves to the supply lines;

[0079]a step for adjusting the fuel-spraying nozzles to be variable and
the oxygen-containing-gas spraying nozzles so that each spraying
direction is in a neighborhood of a tangential direction of the inner
circumferential wall of the combustion chamber, to control combustion;
and

[0080]a step for controlling on/off of the switching valves so that the
spraying speed from the nozzles is maintained in a predetermined range
corresponding to the combustion load applied to the tubular flame burner.

[0081]Eleventh, a method for controlling combustion by a tubular flame
burner comprises:

[0082]a step for preparing a tubular combustion chamber wherein the
front-end opens, and a plurality of fuel-spraying nozzles and a plurality
of oxygen-containing-gas spraying nozzles, wherein each nozzle orifice
faces the inner wall of the combustion chamber;

[0083]a step for connecting supply lines to the nozzles, and for providing
switching valves to the supply lines;

[0084]a step for adjusting the fuel-spraying nozzles and the
oxygen-containing-gas spraying nozzles so that each spraying direction is
in a neighborhood of a tangential direction of the inner circumferential
wall of the combustion chamber, to control combustion;

[0085]a step for controlling on/off of the switching valves so that the
spraying speed from the nozzles is maintained in a predetermined range
corresponding to the combustion load applied to the tubular flame burner;
and

[0086]a step for adjusting the apertures area of the nozzle orifices so
that the spraying speed from the nozzles is maintained in a predetermined
range corresponding to the combustion load applied to the tubular flame
burner by adjusting means for adjusting the apertures area of the nozzle
orifices.

[0087]Twelfth, a method for controlling combustion by a tubular flame
burner comprises: [0088]a step for preparing: a tubular combustion
chamber whose front-end opens, and a plurality of nozzles whose each
nozzle orifice faces the inner wall of the combustion chamber, for
spraying a premixed gas formed of a fuel gas and an
oxygen-containing-gas; [0089]a step for connecting supply lines to the
nozzles, and providing switching valves to the supply lines; [0090]a step
for adjusting the nozzles so that each spraying direction is in a
neighborhood of a tangential direction of the inner circumferential wall
of the combustion chamber, to control combustion; [0091]a step for
controlling on/off of the switching valves so that the spraying speed
from the nozzles is maintained in a predetermined range corresponding to
the combustion load applied to the tubular flame burner; and, [0092]a
step for adjusting the apertures area of the nozzle orifices so that the
spraying speed from the nozzles is maintained in a predetermined range
corresponding to the combustion load applied to the tubular flame burner
by adjusting means for adjusting the apertures of the nozzle orifices.

[0093]Thirteenth, a method for controlling combustion by a tubular flame
burner comprises: [0094]a step for preparing a tubular combustion
chamber whose front-end opens, and whose respective nozzle orifice faces
the inner wall of the combustion chamber for separately spraying fuel and
an oxygen-containing-gas, or spraying a premixed gas thereof; [0095]a
step for preparing a multi-stage tubular flame burner including a
plurality of tubular flame burners that have the respective nozzles,
wherein each spraying direction is in a neighborhood of a tangential
direction of the inner circumferential wall of the combustion chamber,
and having a configuration wherein the rear-end of the tubular flame
burner with a longer inner diameter of the combustion chamber is
connected to the front-end of the tubular flame burner with a shorter
inner diameter of the combustion chamber, whereby the single multi-stage
tubular flame burner is formed of the plurality of tubular flame burners;
and [0096]a step for controlling combustion by selecting a tubular flame
burner to be used within the plurality of tubular flame burners forming
the multi-stage tubular flame burner corresponding to the combustion
load.

[0097]Fourteenth, a method for controlling combustion by a tubular flame
burner comprises: [0098]a step for preparing a tubular combustion
chamber formed of an inner tube, and an outer tube disposed along the
outer circumferential wall of the inner tube, wherein the front-end
opens, and for preparing fuel spraying nozzles and oxygen-containing-gas,
wherein each nozzle orifice are formed on the inner face of the
combustion chamber; [0099]a step for adjusting the nozzles so that each
spraying direction is in a neighborhood of a tangential direction of the
inner circumferential wall of the combustion chamber; [0100]a step for
adjusting the length of the combustion chamber by sliding the outer tube;
[0101]wherein the outer tube has a combustion chamber whose length is
long enough to generate the flame in the combustion chamber in order for
the furnace temperature to reach a predetermined temperature, and
further, the outer tube has a combustion chamber whose length is short
enough to generate the flame outside the combustion chamber when the
in-furnace temperature exceeds the predetermined temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

[0102]FIG. 1 is a side view of a tubular flame burner according to an
embodiment of the present invention.

[0103]FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1.

[0104]FIG. 3 is an explanatory diagram for describing ignition with a
tubular flame burner according to an embodiment of the present invention.

[0105]FIG. 4 is a longitudinal cross-sectional view, which shows a tubular
flame burner according to an embodiment of the present invention.

[0106]FIG. 5 is a diagram which shows the whole length L1 of the
tube-shaped flame formed within the combustion chamber and the length
L2 of the tube-shaped flame formed on the inside and the outside of
the combustion chamber.

[0107]FIG. 6 is a chart, which shows the relation between L2/L1,
the heat transfer amount, and the amount of created soot.

[0108]FIG. 7 is a chart, which shows the relation between L2/L1
and the amount of created NOx.

[0109]FIG. 8A is an explanatory diagram for describing a conventional
tubular flame burner, and is also a configuration diagram of the tubular
flame burner.

[0110]FIG. 8B is a cross-sectional view taken along line B-B in FIG. 8A.

[0111]FIG. 9 is a chart, which shows the furnace temperature and the
temperature of heated steel over time, obtained from a combustion test
according to the present invention.

[0112]FIG. 10 is a chart, which shows the concentration of NOx and
soot over time, obtained from a combustion test according to the present
invention.

[0113]FIG. 11 is a chart, which shows the concentration of NOx over
time according to the present invention.

[0114]FIG. 12 is a chart, which shows the concentration of soot over time
according to the present invention.

[0115]FIG. 13 is a side view of a multi-stage tubular flame burner
according to an embodiment of the present invention.

[0116]FIG. 14A is a cross-sectional view taken along line A-A in FIG. 13.

[0117]FIG. 14B is a cross-sectional view taken along line B-B in FIG. 13.

[0118]FIG. 15 is an explanatory diagram for describing a combustion
control method for a multi-stage tubular flame burner according to an
embodiment of the present invention.

[0119]FIG. 16 is an explanatory diagram for describing a combustion
control method for a multi-stage tubular flame burner according to an
embodiment of the present invention.

[0120]FIG. 17 is an explanatory diagram for describing a combustion
control method for a multi-stage tubular flame burner according to an
embodiment of the present invention.

[0121]FIG. 18A is an explanatory diagram for describing a tubular flame
burner according to an embodiment of the present invention, and is also a
configuration diagram of the tubular flame burner.

[0122]FIG. 18B is an explanatory diagram for describing a tubular flame
burner according to an embodiment of the present invention, and is also a
cross-sectional view taken along line B-B in FIG. 18A.

[0123]FIG. 19 is a side view of a tubular flame burner according to an
embodiment of the present invention.

[0124]FIG. 20A is a cross-sectional view taken along line A-A in FIG. 19.

[0125]FIG. 20B is a cross-sectional view taken along line B-B in FIG. 19.

[0126]FIG. 21 is an overall configuration diagram, which shows a
combustion controller for a tubular flame burner according to an
embodiment of the present invention.

[0127]FIG. 22A is an explanatory diagram for describing a combustion
control method according to an embodiment of the present invention.

[0128]FIG. 22B is an explanatory diagram for describing a combustion
control method according to an embodiment of the present invention.

[0129]FIG. 23 is a side view of a tubular flame burner according to an
embodiment of the present invention.

[0130]FIG. 24A is a cross-sectional view taken along line A-A in FIG. 23.

[0131]FIG. 24B is a cross-sectional view taken along line B-B in FIG. 23.

[0132]FIG. 25 is an overall configuration diagram, which shows a
combustion controller for a tubular flame burner according to an
embodiment of the present invention.

[0133]FIG. 26 is an overall configuration diagram, which shows a
combustion controller for a tubular flame burner according to an
embodiment of the present invention.

[0134]FIG. 27 is an overall configuration diagram, which shows a
combustion controller for a tubular flame burner according to an
embodiment of the present invention.

[0135]FIG. 28 is a side view of a tubular flame burner according to an
embodiment of the present invention.

[0136]FIG. 29A is a cross-sectional view taken along line A-A in FIG. 28.

[0137]FIG. 29B is a cross-sectional view taken along line B-B in FIG. 28.

[0138]FIG. 30 is an overall configuration diagram, which shows a
combustion controller for a tubular flame burner according to an
embodiment of the present invention.

[0139]FIG. 31A is an explanatory diagram for describing a combustion
control method according to an embodiment of the present invention.

[0140]FIG. 31B is an explanatory diagram for describing a combustion
control method according to an embodiment of the present invention.

PREFERABLE EMBODIMENT OF THE INVENTION

First Embodiment

[0141]FIG. 1 through FIG. 3 show a first embodiment of the present
invention. FIG. 1 is a side view of a tubular flame burner according to
the present embodiment, and FIG. 2 is a cross-sectional view taken along
line A-A in FIG. 1. FIG. 3 is an explanatory diagram for describing
ignition of the tubular burner according to the present embodiment.

[0142]In FIG. 1, reference numeral 10 denotes a tubular combustion
chamber, wherein the front-end 10a opens so as to serve as an exhaust
vent for an exhaust gas. Furthermore, the tubular combustion chamber 10
includes nozzles near the rear-end 10b thereof for spraying fuel gas and
oxygen-containing-gas into the tubular combustion chamber 10.
Furthermore, the tubular combustion chamber 10 includes an ignition spark
plug 21 on the rear-end 10b thereof for generating a spark within the
combustion chamber 10 using an igniter 22 and a power supply 23.

[0143]As shown in FIG. 1 and FIG. 2, four long and narrow slits 12 are
formed along the tube axis on the circumferential of the tubular
combustion chamber 10, serving as nozzles for the combustion chamber 10,
wherein the slits 12 are connected to nozzles 11a, 11b, 11c, and 11d,
formed flat and long and narrow along the tube axis, respectively. These
nozzles 11a, 11b, 11c, and 11d, are disposed so that each spray direction
is in a tangential direction of the inner circumferential wall of the
combustion chamber 10 so as to form a swirl in a predetermined direction.
Of these four nozzles, the nozzles 11a and 11c serve as fuel-gas spraying
nozzles, and the nozzles 11b and 11d serve as oxygen-containing-gas
spraying nozzles.

[0144]That is to say, the fuel-gas spraying nozzles 11a and 11c spray the
fuel gas toward the tangential direction of the inner circumferential
wall of the combustion chamber 10 at a high speed, and the
oxygen-containing-gas spraying nozzles 11b and 11d spray the
oxygen-containing-gas toward the tangential direction of the inner
circumferential wall of the combustion chamber 10 at a high speed, so as
to form a swirl while efficiently mixing the fuel gas and the
oxygen-containing-gas at a region near the inner circumferential wall of
the combustion chamber 10. The mixture gas forming such a swirl is
suitably ignited by the ignition spark plug 21 so as to form a
tube-shaped flame within the combustion chamber 10. Note that a
combustion gas is discharged from the front-end 10a of the combustion
chamber 10a.

[0145]Note that the aforementioned oxygen-containing-gas represents a gas
for carrying oxygen used for combustion such as air, oxygen,
oxygen-enriched air, exhaust mixture gas, or the like.

[0146]With the present embodiment, the ignition spark plug 21 is disposed
at a position between the tube axis of the combustion chamber 10 and a
position away therefrom by r/2 (note that r denotes the radius of the
combustion chamber).

[0147]FIG. 3 shows the relation between the mounting position of the
ignition spark plug 21 along the radius direction of the combustion
chamber 10 and the ignition state using the ignition spark plug 21. This
illustrates that the combustion chamber 10 including the ignition spark
plug 21 at a position between the tube axis and the position away
therefrom by r/2 exhibits excellent ignition.

[0148]The reason why the flow speed of the swirl of the mixture gas of the
fuel gas and the oxygen-containing-gas is relatively small near the tube
axis of the combustion chamber 10, thereby effecting a mixture gas in a
suitable range, and thereby enabling ignition definitely to be stable.

[0149]Thus, the tubular flame burner according to the present embodiment
does not require any pilot burner for ignition, thereby reducing the size
and costs thereof.

[0150]Furthermore, in case that the tubular flame burner has a
configuration, that is, a reduced distance L between each of the nozzles
11a through 11d and the rear-end 10b of the combustion chamber 10, in
order to further reduce the size thereof, the distance L is insufficient
for mixing the fuel gas and the oxygen-containing-gas. Because, it leads
to a problem that the region where gas fuel and oxygen-containing fuel
are mixed in a suitable range of the air excess ratio may be reduced in
the radius direction near the rear-end 10b of the combustion chamber 10.
Accordingly, the ignition spark plug 21 is preferably disposed at a
position between the tube axis and the position away therefrom by r/3.
Thus, even in case of the tubular flame burner having such a
configuration wherein the nozzles 11a through lid are disposed close to
the ignition spark plug 21 (L≈0), excellent ignition can be done
in a definite way to be stable.

[0151]Note that while description has been made in the present embodiment
regarding the arrangement wherein each of the fuel-gas spraying nozzles
and the oxygen-containing-gas spraying nozzles are disposed so that each
spraying direction matches with the tangential direction of the inner
circumferential wall of the combustion chamber, an arrangement according
to the present invention is not restricted to the arrangement wherein
each spraying direction matches with the tangential direction thereof. It
may be a case, an arrangement is made wherein each spraying direction
does not match with the tangential direction of the inner circumferential
wall of the combustion chamber as long as a swirl of the gas is formed
within the combustion chamber.

[0152]Furthermore, while description has been made in the present
embodiment regarding the arrangement wherein the slits serving as the
nozzles for the combustion chamber are disposed along the tube axis, and
each slit is connected to the corresponding flat fuel-gas spraying nozzle
or oxygen-containing spraying nozzle, an arrangement may be made, wherein
multiple small-sized openings forming a nozzle orifice for the combustion
chamber are formed along the tube axis, and each nozzle is connected to
the corresponding array formed of the small-sized openings for spraying
the fuel gas or the oxygen-containing-gas.

[0153]Furthermore, description has been made in the present embodiment
regarding the arrangement wherein the fuel gas is sprayed, an arrangement
may be made wherein liquid fuel is sprayed. Note that kerosene, gas oil,
alcohol, A-type heavy oil, or the like, which readily evaporates under
relatively low temperature, is suitably employed as the liquid fuel.

[0154]Furthermore, description has been made in the present embodiment
regarding the arrangement wherein the fuel gas and the
oxygen-containing-gas are separately sprayed, an arrangement may be made
wherein a mixture gas formed by premixing the fuel gas and the
oxygen-containing-gas is sprayed.

[0155]In case of the tubular flame burner according to the present
embodiment, the ignition spark plug is disposed at a suitable position
near the tube axis of the combustion chamber, thereby performing ignition
of a mixture gas of the fuel gas and the oxygen-containing-gas within the
combustion camber in a definite way to be stable. And furthermore, the
tubular flame burner according to the present embodiment requires no
ignition pilot burner, thereby reducing the size and costs thereof.

[0156]Note that the tubular flame burner according to the present
embodiment may be also formed with a polygonal cross-sectional shape
rather than round.

Second Embodiment

Embodiment 2-1

[0157]Description will be made regarding a second embodiment of the
present invention with reference to the drawings. FIG. 4 is a
longitudinal cross-sectional diagram, which shows a tubular flame burner
according to the present embodiment.

[0158]The tubular flame burner comprises a combustion chamber 103 formed
of an inner tube 101 of which one end opens, and an outer tube 102
wherein both ends opens, and which can be slid along the outer
circumferential wall of the inner tube 101, a fuel-spraying nozzle 104
and an oxygen-containing-gas-spraying nozzle 105, wherein a nozzle
orifice of each is formed on the inner face of the inner tube 101 of the
aforementioned combustion chamber 103.

[0159]Note that the fuel-spraying nozzle 104 and the
oxygen-containing-gas-spraying nozzle 105 are connected so that each
spraying direction generally matches the tangential direction of the
inner circumferential wall of the combustion chamber 103 as viewed in the
diameter direction of the combustion chamber 103. Note that the
oxygen-containing-gas represents a gas for carrying oxygen used for
combustion such as air, oxygen, oxygen-enriched air, exhaust mixture gas,
or the like.

[0160]With such a configuration, the fuel is sprayed from the
fuel-spraying nozzle 104 into the combustion chamber 103 as well as
spraying the oxygen-containing-gas from the
oxygen-containing-gas-spraying nozzle 105, and ignition is made by the
ignition plug 106, whereby a tube-shaped flame is formed along the inner
circumferential wall of the inner tube 101 of the combustion chamber 103.
The flame thus formed is referred to as a tube-shaped flame 107.

[0161]While in general, a tubular flame burner is designed so that
combustion of the tube-shaped flame 107 is made within the combustion
chamber 103, with the tubular flame burner according to the present
invention, a part of the tube-shaped flame 107 can be formed on the
outside of the inner tube 101, wherein in the event that the outer tube
102 is slid so as to extend the combustion chamber 103, the entire
tube-shaped flame 107 is formed within the combustion chamber 103. And on
the other hand, in the event that the outer tube 102 is slid so as to
collapse the combustion chamber 103, a part of the tube-shaped flame 107
is formed on the outside of the combustion camber 103.

[0162]The lengths of the inner tube 101 and the outer tube 102 may be
experimentally determined as well as being theoretically determined.

[0163]With the entire length of the tube-shaped flame 107 thus formed as
L1, and with the length of the tube-shaped flame 107 formed on the
outside of the combustion chamber 103 as L2, as shown in FIG. 5, the
greater the value L2/L1 is, the greater the heat transfer
amount and the amount of created soot are, as shown in the chart in FIG.
6. The reason why is that the increased L2 causes an increase of the
ratio of a luminous flame, and accordingly, the ratio of stable
combustion is reduced within the combustion chamber 103 as well as
promoting heat transfer to the heated object. This results in such a
state that soot is readily generated.

[0164]On the other hand, the greater the L2/L1 is, the smaller
the amount of the created NOx as shown in the chart in FIG. 7. The reason
why is that increased ratio of combustion on the outside of the
combustion chamber 103 within the furnace space leads to
dilution-combustion while swirling an exhaust gas within a space on the
outside of the combustion chamber 103. Accordingly, the concentration of
oxygen is reduced within the combustion space as well as preventing
generation of partial high-temperature region, thereby suppressing
reaction of creation of thermal NOx, and thereby suppressing the amount
of created NOx.

[0165]The tubular flame burner according to the present invention controls
the heat transfer amount, the amount of created soot, and the amount of
the created NOx.

[0166]Note that the tubular flame burner according to the present
embodiment may be also formed with a polygonal cross-sectional shape
rather than round.

Embodiment 2-2

[0167]Combustion testing was performed using the tubular flame burner
according to the present invention.

[0168]FIG. 9 is a chart that shows the in-furnace temperature (curve A)
and the temperature of steel (curve B) over time, which have been
measured in the combustion test. In the aforementioned combustion test,
the in-furnace temperature is raised at a constant temperature increase
rate to 1000° C., and upon reaching 1000° C., the
temperature is maintained at 1000° C. for a total heating time of
15 hours.

[0169]First, steel was heated under the condition that the outer
circumferential wall (denoted by reference numeral 102 in FIG. 4) was
slid toward the inside of the furnace such that L2 shown in FIG. 5
becomes 0 or less, i.e., the flame was formed only within the combustion
chamber (first combustion test). FIG. 10 shows concentration of NOx and
soot over time obtained in the aforementioned combustion test.

[0170]In FIG. 10, an index representation of the concentration thereof is
expressed with the permissive value as 100.

[0171]In such a case, while only a small amount of soot was generated, the
amount of NOx increased up to the concentration of index value 150 over
time until the in-furnace temperature reached 1000° C. And the
concentration of NOx was maintained to the high concentration of index
value 150 after the in-furnace temperature reached 1000° C.
Accordingly, it has been revealed that the aforementioned combustion
leads to a problem of generating a high NOx.

[0172]On the other hand, the measured temperature of the steel after
heating for 15 hours was 950° C., which was considerably lower
than the determined temperature of 1000° C.

[0173]Next, steel was heated under the same conditions as the first
combustion test, except that the outer circumferential wall 102 was slid
away from the inside of the furnace such that L2 shown in FIG. 5
exceeds 0, i.e., a part of the flame was formed outside the combustion
chamber (the second combustion test). FIG. 11 shows the concentration of
NOx and soot over time obtained in the aforementioned combustion test.

[0174]In FIG. 11, an index representation of the concentration is made
with the permissive values as 100. In the aforementioned combustion,
while a somewhat great amount of soot was generated during the
temperature-rising step, the amount of the generated soot became small
after the in-furnace temperature reached 1000° C., which brings up
a little bit problem. On the other hand, the amount of the generated NOx
was suppressed to a low level over all the heating steps. That is to say,
the combustion in such a case causes no problems to generate NOx, while
leading to a small problem of a somewhat great amount of the soot
generated in the temperature-rising step.

[0175]On the other hand, the measured temperature of the steel after
heating for 15 hours was 980° C., which was closer to the
determined temperature of 1000° C., compared with the first
combustion test. It has been revealed that the second combustion method
exhibits more efficient heating of steel than with the first combustion
method, except for generating the soot at a low temperature.

[0176]Next, steel was heated under the combination of heating conditions
for the first and second combustion test. This was done for the
in-furnace temperature to be as the same as the second combustion test,
that is, after the in-furnace temperature exceeded 800° C., a part
of the flame was formed on the outside of the combustion chamber. This
resulted in suppressing the amount of the generated soot and NOx to an
extent of the permissive values or less. These were done, based on the
results from the first and second combustion tests (third combustion
test).

[0177]FIG. 12 shows concentration of NOx and soot over time obtained in
the aforementioned combustion test.

[0178]In FIG. 12, an index representation of the concentration thereof is
made with the permissive values as 100 in the same way. In the
aforementioned combustion, both the amount of the generated soot and that
of the generated NOx exists in a stable condition, resulting in
suppressing the concentration values to low levels. In such a way, the
amount of the generated soot is suppressed to an extent of the
concentration value, 30 or less. And the amount of the generated NOx is
suppressed to an extent of the concentration value, 80 or less over all
the heating steps, whereby excellent heating is achieved.

[0179]On the other hand, when the steel temperature was measured after
heated for 15 hours, it was 975° C. And it has been revealed that
efficient heating was achieved in the third combustion test, while the
temperature of steel was somewhat lower than that in the second
combustion test.

[0180]As described above, it has been revealed that the combustion by a
fixed and constant length of the combustion chamber of the tubular flame
burner leads to a problem of generating soot at a low in-furnace
temperature. And it leads to a problem of generating NOx at a high
temperature therein. On the contrary, by adjusting the length of the
combustion chamber corresponding to the in-furnace temperature, the steel
can be heated in a good and an excellent way.

Third Embodiment

Embodiment 3-1

[0181]FIG. 13 through FIG. 16 show a multi-stage tubular flame burner
according to an embodiment of the present invention. FIG. 13 is a side
view of the multi-stage tubular flame burner according to the present
embodiment. FIG. 14A is a cross-sectional view taken line A-A in FIG. 13.
FIG. 14B is a cross-sectional view taken line B-B in FIG. 13. FIG. 15 and
FIG. 16 are explanatory diagrams, which describes a method for
controlling combustion by the multi-stage tubular flame burner according
to the present embodiment.

[0182]In FIG. 13, reference numeral 201 denotes the multi-stage tubular
flame burner according to the present embodiment. FIG. 13 has such a
configuration that a small-diameter flame burner 213 with a small inner
diameter is connected to the rear-end of a large-diameter flame burner
202 with a large inner diameter in series, so as to form a single tubular
flame burner.

[0183]The large-diameter tubular flame burner 202 includes a tubular
combustion chamber 210, whose one end 210a opens for serving as an
exhaust vent for a combustion gas, and nozzles 211a, 211b, 211c, and
211d, for separately spraying a fuel gas and an oxygen-containing-gas
into the combustion chamber 210. Long and narrow slits 212 are formed at
the four parts. Here, the four parts are located on the same single
circumference of the combustion chamber 210, and these slits are located
at the neighborhood of the rear-end 210b of the combustion chamber 210,
in order to serve them as nozzle orifices for the combustion chamber 210.
And these slits 212 are connected to nozzles 211a, 211b, 211c, and 211d,
as being formed flat, being long and narrow along the tube axis,
respectively. The nozzles 211a, 211b, 211c, and 211d, are disposed so
that the spraying direction of each is in a tangential direction of the
inner circumferential wall of the combustion chamber 210, so as to cause
a swirl in a single rotational direction. Of these four nozzles, two
nozzles of the nozzles 211a and 211c serve as fuel-gas-spraying nozzles,
and the rested two nozzles of these four nozzles, 211b and 211d serve as
oxygen-containing-gas-spraying nozzles.

[0184]The fuel-gas-spraying nozzles 211a and 211c spray a fuel gas in the
tangential direction of the inner circumferential wall of the combustion
chamber 210 at a high speed, as well as the
oxygen-containing-gas-spraying nozzles 211b and 211d spraying an
oxygen-containing-gas in the tangential direction of the inner
circumferential wall of the combustion chamber 210 at a high speed, so as
to form a swirl while efficiently mixing the fuel gas and the
oxygen-containing-gas at a region near the inner circumferential wall of
the combustion chamber 210. Upon ignition of the mixture gas forming a
swirl by an ignition device (not shown) such as an ignition plug, pilot
burner, or the like, a tube-shaped flame is formed within the combustion
chamber 210. A combustion gas is discharged from the front-end 210a of
the combustion chamber 210.

[0185]On the other hand, as shown in FIG. 13 and FIG. 14B, the
small-diameter tubular flame burner 203 includes a tubular combustion
chamber 213 having a configuration. Here, the front-end 213a is connected
to the rear-end 210b of the large-diameter tubular flame burner 202, so
as to serve as an exhaust vent for a combustion gas, and nozzles 214a,
214b, 214c, and 214d, for separately spraying a fuel gas and an
oxygen-containing-gas into the combustion chamber 213. Long and narrow
slits 215 are formed at the respective four parts, on the same single
circumference of the combustion chamber 213. They are located at the
neighborhood of the rear-end 213b of the combustion chamber 213 for
serving as nozzle orifices for the combustion chamber 213. Here, these
slits 215 are connected to nozzles 214a, 214b, 214c, and 214d, as being
flat, long and narrow along the tube axis, respectively. The respective
nozzles 214a, 214b, 214c, and 214d, are disposed so that the spraying
direction of each is in a tangential direction of the inner
circumferential wall of the combustion chamber 213, so as to cause a
swirl in a single rotational direction. Of these four nozzles, two
nozzles, 214a and 214c, serve as fuel-gas-spraying nozzles, and the
rested two nozzles of these nozzles, 214b and 214d, serve as
oxygen-containing-gas-spraying nozzles.

[0186]Note that the slits 212 of the large-diameter tubular flame burner
202 are formed with the area of each orifice larger than the slits 215 of
the small-diameter tubular flame burner 203 corresponding to a larger
inner diameter of the combustion chamber 210 of the large-diameter
tubular flame burner 202.

[0187]The fuel-gas-spraying nozzles 214a and 214c spray a fuel gas in the
tangential direction of the inner circumferential wall of the combustion
chamber 213 at a high speed, as well as the
oxygen-containing-gas-spraying nozzles 214b and 214d spraying an
oxygen-containing-gas in the tangential direction of the inner
circumferential wall of the combustion chamber 213 at a high speed, so as
to form a swirl while efficiently mixing the fuel gas and the
oxygen-containing-gas at a region near the inner circumferential wall of
the combustion chamber 213. Upon igniting the mixture gas forming a swirl
by an ignition device (not shown) such as an ignition plug, pilot burner,
or the like, a tube-shaped flame is formed within the combustion chamber
213. A combustion gas is discharged from the front-end 210a through the
front-end 213a of the combustion chamber 213 and the combustion chamber
210 of the large-diameter tubular flame burner 202.

[0188]Note that the oxygen-containing-gas represents a gas for carrying
oxygen used for combustion such as air, oxygen, oxygen-enriched air,
exhaust mixture gas, or the like.

[0189]Furthermore, as shown in FIG. 15, an switching valve 216a for
switching supply of the fuel gas to the nozzles 211a and 211c is disposed
at a portion on a line for supplying the fuel gas to the
fuel-gas-spraying nozzles 211a and 211c of the large-diameter tubular
flame burner 202, and an switching valve 216b for switching supply of the
oxygen-containing-gas to the nozzles 211b and 211d is disposed at a
portion on a line for supplying the oxygen-containing-gas to the
fuel-gas-spraying nozzles 211b and 211d of the large-diameter tubular
flame burner 202. Thus, switching is performed between use and stop of
the large-diameter tubular flame burner 202 by switching the switching
valves 216a and 216b.

[0190]Furthermore, an switching valve 217a for switching supply of the
fuel gas to the nozzles 214a and 214c is disposed at a portion on a line
for supplying the fuel gas to the fuel-gas-spraying nozzles 214a and 214c
of the small-diameter tubular flame burner 203, and an switching valve
217b for switching supply of the oxygen-containing-gas to the nozzles
214b and 214d is disposed at a portion on a line for supplying the
oxygen-containing-gas to the fuel-gas-spraying nozzles 214b and 214d of
the large-diameter tubular flame burner 203. Thus, switching is performed
between use and stop of the small-diameter tubular flame burner 203 by
switching the switching valves 217a and 217b.

[0191]Furthermore, a supply controller 220 is provided for controlling
on/off of the switching valves 216a, 216b, 217a, and 217b, whereby the
tubular flame burner to be used is selected for use by the on/off control
thereof.

[0192]Furthermore, a fuel-gas-flow regulator 218 for adjusting the total
flow of the fuel gas to be supplied to the fuel-gas-spraying nozzles
211a, 211c, 214a, and 214c, is disposed on a line for supplying the fuel
gas, and an oxygen-containing-gas-flow regulator 219 for adjusting the
total flow of the oxygen-containing-gas to be supplied to the
oxygen-containing-gas-spraying nozzles 211b, 211d, 214b, and 214d, is
disposed on a line for supplying the oxygen-containing-gas. The supply
controller 220 controls the fuel-gas-flow regulator 218 and the
oxygen-containing-gas-flow regulator 219 so as to control the total flow
of supplied fuel gas and oxygen-containing-gas.

[0193]Note that the total supply flow of the fuel gas and the
oxygen-containing-gas is measured by a flow-meter 221 for the fuel gas
and a flow-meter 222 for the oxygen-containing-gas, and the measurement
value is sent to the supply controller 220 so as to be used for adjusting
the apertures of the fuel-gas-flow regulator 218 and the
oxygen-containing-gas-flow regulator 219.

[0194]Description will be made below regarding a method for controlling
combustion by the multi-stage tubular flame burner 201 having such a
configuration with reference to FIG. 15 and FIG. 16.

[0195]With the combustion control method for the multi-stage tubular flame
burner, a desired tubular flame burner is selected for combustion from
the large-diameter tubular flame burner 202 and the small-diameter
tubular flame burner 203 corresponding to the combustion load.

[0196]That is to say, each of the large-diameter tubular flame burner 202
and the small-diameter tubular flame burner 203 has a particular possible
range of combustion. That is, a particular range of the combustion load,
corresponding to the range of supply flow between the minimal
flame-formation flow speed required for forming a tubular flame and the
maximal permissive flow speed dependent upon the pressure loss. Here, the
small-diameter tubular flame burner 203 is formed with a small inner
diameter of the combustion chamber and a small aperture area of the
slits. Accordingly, it has a possible range of combustion corresponding
to a range of a small combustion load, and on the other hand, the
large-diameter tubular flame burner 202 is formed with a large inner
diameter of the combustion chamber and a large aperture area of the
slits, and accordingly has a possible range of combustion corresponding
to a range of a relatively large combustion load.

[0197]Thus, in case of a small combustion load, the small-diameter tubular
flame burner 203 is used. And in the event that the combustion load
becomes greater, the large-diameter tubular flame burner 202 is used. And
in the event that the combustion load becomes much greater, both the
large-diameter tubular flame burner 202 and the small-diameter tubular
flame burner 203 are used.

[0198]Thus, the multi-stage tubular flame burner according to the present
embodiment enables stable combustion to be in a wide range of the
combustion load, which is difficult for a single-diameter tubular flame
burner.

[0199]Note that the tubular flame burner according to the present
embodiment may also be formed with a polygonal cross-sectional shape,
rather than round.

Embodiment 3-2

[0200]Next, description will be made regarding another embodiment with
reference to FIG. 17.

[0201]In the previous embodiment, as shown in FIG. 15, the multi-stage
tubular flame burner has a configuration for adjusting the total flow of
the fuel gas and the total flow of the oxygen-containing-gas to be
supplied to the tubular flame burner that has a large diameter, and/or
the tubular flame burner that has a small-diameter. An arrangement
according to the present embodiment has a configuration for further
adjusting the total flow of the fuel gas and the total flow of the
oxygen-containing-gas to be supplied for each of the large-diameter
tubular flame burner 210 and the small-diameter tubular flame burner 213.

[0202]That is to say, as shown in FIG. 17, first, a fuel-gas-flow
regulator 218a for adjusting the flow of the fuel gas to be supplied to
the fuel-gas-spraying nozzles 211a and 211c is provided on a line for
supplying the fuel gas to the tubular flame burner 210 that has a
large-diameter, and furthermore, an oxygen-containing-gas-flow regulator
219a for adjusting the flow of the oxygen-containing-gas to be supplied
to the oxygen-containing-gas-spraying nozzles 211b and 211d is provided
on a line for supplying the oxygen-containing-gas to the tubular flame
burner that has a large-diameter 210. The supply controller 220a adjusts
the fuel-gas-flow regulator 218a and the oxygen-gas-flow regulator 219a,
so as to control each of the fuel-gas flow and the oxygen-containing-gas
flow to be supplied to the large-diameter tubular flame burner. The
supply flow of the fuel gas and the supply flow of the
oxygen-containing-gas are measured by a fuel-gas flow-meter 221a and an
oxygen-containing-gas flow-meter 222a, respectively. And the measurement
values are sent to the supply controller 220a, so as to be used for
aperture adjustment of the fuel-gas-flow regulator 218a and the
oxygen-containing-gas-flow regulator 219a.

[0203]In the same way, a fuel-gas-flow regulator 218b for adjusting the
flow of the fuel gas to be supplied to the fuel-gas-spraying nozzles 214a
and 214c is provided on a line for supplying the fuel gas to the
small-diameter tubular flame burner 213. And furthermore, an
oxygen-containing-gas-flow regulator 219b for adjusting the flow of the
oxygen-containing-gas to be supplied to the
oxygen-containing-gas-spraying nozzles 214b and 214d is provided on a
line for supplying the oxygen-containing-gas to the small-diameter
tubular flame burner 213. The supply controller 220b adjusts the
fuel-gas-flow regulator 218b and the oxygen-gas-flow regulator 219b, so
as to control each of the fuel-gas flow and the oxygen-containing-gas
flow to be supplied to the small-diameter tubular flame burner 213. The
supply flow of the fuel gas and the supply flow of the
oxygen-containing-gas are measured by a fuel-gas flow-meter 221b and an
oxygen-containing-gas flow-meter 222b, respectively. And the measurement
values are sent to the supply controller 220b so as to be used for
aperture adjustment of the fuel-gas-flow regulator 218b and the
oxygen-containing-gas-flow regulator 219b.

[0204]The supply controller 220a for the large-diameter tubular flame
burner 210 and the supply controller b for the small-diameter tubular
flame burner 213 are interconnected each other for adjusting the total
supply flow of the fuel gas and the oxygen-containing-gas.

[0205]In case of a small combustion load, using the multi-stage tubular
flame burner having such a configuration and doing the combustion, each
of the apertures are adjusted corresponding to the combustion state.
(Here, each of the apertures exists between the fuel-gas-flow regulator
218b and the oxygen-containing-gas-flow regulator 219b of the tubular
flame burner 213 that has the small diameter. Here, each of the apertures
is determined and adjusted to be zero, wherein the respective apertures
exist between the fuel-gas-flow regulator 218a and the
oxygen-containing-gas-flow regulator 219a of the tubular flame burner 210
that has a large-diameter. And, in the event that the combustion load
becomes greater, each of the apertures of the fuel-gas-flow regulator
218a and the oxygen-containing-gas-flow regulator 219a of the
large-diameter tubular flame burner 210 are adjusted corresponding to the
combustion state. In this case, each of the apertures of the
fuel-gas-flow regulator 218b is set to be zero, wherein each of the
apertures exist between the oxygen-containing-gas-flow regulator 219b of
the small-diameter tubular flame burner 213. Furthermore, in the event
that the combustion load becomes more greater, the apertures of the
fuel-gas-flow regulator 218b and the oxygen-containing-gas-flow regulator
219b of the small-diameter tubular flame burner 213, which have been
determined to be zero, open. The fuel-gas-flow regulator 219b of the
large-diameter tubular flame burner 210 opens corresponding to the
combustion load. And concerning the apertures of the fuel-gas-flow
regulator 218a and the oxygen-containing-gas-flow regulator 219a of the
large-diameter tubular flame burner 210 and the apertures of the
fuel-gas-flow regulator 218b and the oxygen-containing-gas-flow regulator
219b of the small-diameter tubular flame burner 213, they are as follows.
That is, both of the apertures are adjusted respectively, corresponding
to the combustion load.

[0206]Thus, the multi-stage tubular flame burner according to the present
embodiment enables stable combustion to exist within a wide range of the
combustion load, which is hard to be applied to a single-diameter tubular
flame burner.

[0207]Up to now, in the above-described embodiments, description has been
made regarding the arrangement that has a configuration so that two
tubular flame burners are connected. But, it may be a case, another
arrangement is made to have a configuration, wherein three or more
tubular flame burners are connected, in accordance with the respective
requirements.

[0208]Furthermore, description has been made in the above-described
embodiments regarding the arrangement, wherein the fuel-gas-spraying
nozzles and the oxygen-containing-gas-spraying nozzles are disposed so
that each spraying direction is in a tangential direction of the inner
circumferential wall of the combustion chamber. However, an arrangement
according to the present invention is not always applied to the
aforementioned one. It may be a case, an arrangement is applied to that
any spraying direction is not in a tangential direction of the inner
circumferential wall of the combustion chamber as long as a swirl of a
mixture gas is formed within the combustion chamber.

[0209]Furthermore, description has been made in the above-described
embodiments regarding the arrangement, wherein the slits serving as the
nozzles for the combustion chamber are disposed along the tube axis, and
wherein each slit is connected to the corresponding flat fuel-gas
spraying nozzle or oxygen-containing spraying nozzle. But, it may be a
case, an arrangement is applied to that multiple small-sized openings,
which serve as a nozzle orifice for the combustion chamber, are formed
along the tube axis. And, it may be a case, each nozzle is connected to
the corresponding array formed of the small-sized openings for spraying
the fuel gas or the oxygen-containing-gas.

[0210]Furthermore, description has been made in the present embodiment
regarding the arrangement, wherein the fuel gas and the
oxygen-containing-gas are separately sprayed. However, it may be a case,
an arrangement is applied to another way, that is, a mixture gas formed
by premixing the fuel gas and the oxygen-containing-gas is sprayed.

[0211]According to the present embodiment, when the multi-stage tubular
flame burner is used, a suitable tubular flame burner is used selectively
for combustion corresponding to the variable increasing/decreasing
combustion load, resulting in making it possible to keep a stable
combustion in_accordance with a wide range of the combustion load.

[0212]The tubular flame burner according to the present embodiment may
also be formed with a polygonal cross-sectional shape, rather than round.

Fourth Embodiment

[0213]Description is made regarding to a tubular flame burner according to
the fourth embodiment of the present invention, referencing to the
drawings. FIG. 18A is a configuration diagram of the tubular flame
burner, and FIG. 18B is a view taken along line B-B in FIG. 18A.

[0214]The tubular flame burner includes a tubular combustion chamber 301
whose one-end opens and nozzles 304 for spraying a fuel gas and an
oxygen-containing-gas. Here, each nozzle orifice of the nozzles is formed
on the inner face of the aforementioned combustion chamber 301. It is
disposed so that each spraying direction is in a neighborhood of a
tangential direction of the inner circumferential wall of such a
configuration that the combustion chamber 301 is combustion chamber 301.
And the tubular flame burner has covered with an outer tube 302, which
has a greater outer diameter than that of the combustion chamber 301.
This is as a role to form a space between the outer face of the
combustion chamber 301 and the inner face of the outer tube 302. Here,
the space between the outer face and the inner face serves as a flow path
303 for a fuel gas or an oxygen-containing-gas. The path is provided
before being supplied to the aforementioned spraying nozzle, as well as
forming the combustion chamber 301 with a greater length than that of a
tube-shaped flame formed therein.

[0215]One end of the combustion chamber 301 opens for serving as an
exhaust vent for a combustion exhaust gas. Furthermore, long slits are
formed on the other end of the combustion chamber 301 along the tube
axis, and are connected to nozzles 304 for separately spraying the fuel
gas and the oxygen-containing-gas.

[0216]The nozzles 304 are disposed in a neighborhood of a tangential
direction of the inner circumferential wall of the combustion chamber
301, so as to form a swirl within the combustion chamber 301 due to
spraying of the fuel gas and the oxygen-containing-gas. Note that the tip
of each nozzle 304 is formed flat with a reduced orifice area so as to
spray the fuel gas and the oxygen-containing-gas at a high speed.
Reference numeral 305 denotes an ignition plug.

[0217]The outer tube 302 has closed front-end and rear-one. And the outer
tube has a configuration, wherein a pipe 306 is connected to a portion on
the front-end side of the outer tube 302 for supplying a combustion gas
or an oxygen-containing-gas to a space 303 formed between the combustion
camber 301 and the outer tube 302.

[0218]On the other hand, a pipe 307, connected to one of the
aforementioned nozzle 304, is connected to a portion on the rear-end side
of the outer tube 302, so as to introduce the preheated fuel gas or
oxygen-containing-gas to the nozzle 304. In such a case, when the
preheated fuel gas is supplied, the oxygen-containing-gas before having
been preheated is supplied to the other nozzle 304 that is disposed
thereon. On the other hand, when the preheated oxygen-containing-gas is
supplied, the fuel gas before having been preheated is supplied to the
other nozzle 304 that is disposed thereon.

[0219]The tubular flame burner, according to the present embodiment, has
the same configuration as the conventional tubular flame burners, except
for the above-described configuration, wherein the fuel gas or the
oxygen-containing-gas is preheated, so as to be supplied to the
combustion chamber 301. And the tubular flame burner has the same
combustion mechanism as the conventional tubular flame burners.
Accordingly, detailed description thereof is omitted.

[0220]The tubular flame burner according to the present embodiment is
formed so that the combustion chamber is longer than a tube-shaped flame
formed therewithin. Accordingly, while the front-end of the combustion
chamber becomes high temperature due to the combustion gas, the fuel gas
or oxygen-containing-gas that has a room temperature cools the combustion
chamber. Accordingly, the burner is not damaged due to heat, thereby
improving the life span of the burner. Furthermore, with the tubular
flame burner according to the present embodiment, the fuel gas or
oxygen-containing-gas is preheated, thereby improving combustion
performance, and thereby extending a range of kinds of fuel, which can be
employed for combustion.

[0221]Note that the tubular flame burner according to the present
embodiment may also be formed with a polygonal cross-sectional shape
rather than round.

EXAMPLES

[0222]In order to confirm the effectiveness of the double-tube burner
according to the present embodiment, combustion test was performed, using
fuel that has a low calorific heating value. Note that combustion test
was also performed using a conventional single-tube tubular flame burner
as a comparative example (without preheating of the combustion air or
fuel). A mixture gas formed of only a blast furnace gas or formed by
mixing the blast furnace gas (BFG) with N2 gas or a coke-oven gas
(COG) is employed as the aforementioned fuel gas that has a lower
calorific heating value than that of the blast furnace gas. Table 1 shows
the obtained results.

[0223]Note that the fuel gases having the same components were employed in
the comparative examples 1 through 3 as in the present examples in Table
1.

[0224]As can be clearly understood from Table 1, in case of combustion of
the blast furnace gas, excellent combustion was obtained both in the
present example wherein the combustion air has been preheated, and the
comparative example 1 wherein the combustion air has not been preheated.
But, on the other hand, in case of combustion of a fuel gas with lower
heating value than with the blast furnace gas, poor combustion occurred
in the comparative examples 2 and 3, wherein the combustion air and the
fuel gas have not been preheated. On the contrary, excellent combustion
was obtained in the present examples 2 through 5, wherein the combustion
air or the fuel gas has been preheated.

[0225]Note that examples of the fuel gases with low heat output used in
the present examples 2 and 3 include an exhaust gas from a reducing
atmosphere furnace or a non-oxidizing atmosphere furnace. Such an
untreated exhaust gas cannot be discharged prohibited. Therefore, the
exhaust gas is burned with a dedicated combustion furnace so as to be
discharged into the air. From such a viewpoint, the present embodiment
has such an advantage that double-tube tubular flame furnace enables
combustion to be made using such an exhaust gas as a fuel gas without
requiring a special dedicated combustion furnace.

Fifth Embodiment

Embodiment 5-1

[0226]FIG. 19 through FIG. 22 show an embodiment 5-1 according to the
present invention. FIG. 19 is a side view of a tubular flame burner
according to the present embodiment, FIG. 20A is a cross-sectional view
taken along line A-A in FIG. 19, and FIG. 20B is a cross-sectional view
taken along line B-B in FIG. 19. FIG. 21 is an overall configuration
diagram of a combustion controller for the tubular flame burner according
to the present embodiment, and FIG. 22 is an explanatory diagram for
describing a combustion control method for the tubular flame burner
according to the present embodiment.

[0227]In FIG. 19, reference numeral 410 denotes a tube-shaped combustion
chamber, wherein the front-end 410a opens so as to serve as an exhaust
vent for a combustion exhaust gas. Furthermore, the combustion chamber
410 includes two nozzle-mounting portions A and B on the side of the
rear-end 410b along the tube axis for mounting nozzles for spraying a
fuel gas to the combustion chamber 410, and nozzles for spraying an
oxygen-containing-gas thereto.

[0228]At the nozzle-mounting portion A, four long and narrow slits 412
extending along the tube axis are formed along the circumferential wall
of the combustion chamber 410 so as to serve as nozzles for the
combustion chamber 410. And these slits are connected to nozzles 411a,
411b, 411c, and 411d, formed flat, and long and narrow along the tube
axis, respectively, as shown in FIG. 19 and FIG. 20A. The nozzles 411a,
411b, 411c, and 411d, are disposed so that each spraying direction is in
a tangential direction of the inner circumferential wall of the
combustion chamber 410 so as to cause a swirl to be in a predetermined
rotational direction. Of these four nozzles, the nozzle 411a and the
nozzle 411c serve as fuel-gas-spraying nozzles, and the nozzle 411b and
the nozzle 411d serve as oxygen-containing-gas spraying nozzles.

[0229]The fuel gas is sprayed from the fuel-gas spraying nozzles 411a and
411c in the tangential direction of the inner circumferential wall of the
combustion chamber 410 at a high speed. Such a procedure is as well as
spraying the oxygen-containing-gas from the oxygen-containing-gas
spraying nozzles 411b and 411d in the tangential direction of the inner
circumferential wall of the combustion chamber 410 at a high speed. This
results in forming a swirl while efficiently mixing the fuel gas and the
oxygen-containing-gas at a region near the inner circumferential wall of
the combustion chamber 410. Upon ignition of the mixture gas forming a
swirl by an ignition device (not shown) such as an ignition plug, pilot
burner, or the like, a tube-shaped flame is formed within the combustion
chamber 410.

[0230]In the same way, at the nozzle-mounting portion B, four long and
narrow slits 414 extending along the tube axis are formed along the
circumferential wall of the combustion chamber 410 so as to serve as
nozzles for the combustion chamber 410. These nozzles are connected to
nozzles 413a, 413b, 413c, and 413d, formed flat, and long and narrow
along the tube axis, respectively, as shown in FIG. 19 and FIG. 20B. The
nozzles 413a, 413b, 413c, and 413d, are disposed so that each spraying
direction is in a tangential direction of the inner circumferential wall
of the combustion chamber 410 so as to cause a swirl to be in a
predetermined rotational direction. Of these four nozzles, the nozzle
413a and the nozzle 413c serve as fuel-gas-spraying nozzles, and the
nozzle 413b and the nozzle 413d serve as oxygen-containing-gas spraying
nozzles.

[0231]The fuel gas is sprayed from the fuel-gas spraying nozzles 413a and
413c in the tangential direction of the inner circumferential wall of the
combustion chamber 410 at a high speed. This procedure is done as well as
spraying the oxygen-containing-gas from the oxygen-containing-gas
spraying nozzles 413b and 413d in the tangential direction of the inner
circumferential wall of the combustion chamber 410 at a high speed, so as
to form a swirl while efficiently mixing the fuel gas and the
oxygen-containing-gas at a region near the inner circumferential wall of
the combustion chamber 410. Upon ignition of the mixture gas forming a
swirl by an ignition device (not shown) such as an ignition plug, pilot
burner, or the like, a tube-shaped flame is formed within the combustion
chamber 410.

[0232]As described above, the tubular flame burner according to the
present embodiment includes two nozzle sets along the tube axis. Each of
these ones are formed of two fuel-gas-spraying nozzles and two
oxygen-containing-gas spraying nozzles along the circumference of the
tube, i.e., the tubular flame burner according to the present embodiment
includes four fuel-gas-spraying nozzles and four oxygen-containing-gas
spraying nozzles.

[0233]Note that the oxygen-containing-gas represents a gas for carrying
oxygen used for combustion such as air, oxygen, oxygen-enriched air,
exhaust mixture gas, or the like.

[0234]Furthermore, as shown in FIG. 20, switching valves 415a, 415c, 416a,
and 416c, for controlling on/off of the fuel gas to the nozzles 411a,
411c, 413a, and 413c, respectively, are disposed on lines for supplying
the fuel gas to the fuel-gas spraying nozzles 411a, 411c, 413a, and 413c,
respectively. And switching valves 415b, 415d, 416b, and 416d, for
controlling on/off of the oxygen-containing-gas to the nozzles 411b,
411d, 413b, and 413d, respectively, are disposed on lines for supplying
the oxygen-containing-gas to the oxygen-containing-gas spraying nozzles
411b, 411d, 413b, and 413d, respectively.

[0235]Furthermore, a supply controller 420 is provided for controlling
on/off of the switching valves 415a, 415b, 415c, 415d, 416a, 416b, 416c,
and 416d, so as to select desired nozzles for spraying the fuel gas and
the oxygen-containing-gas to the combustion chamber 410.

[0236]Furthermore, the line for supplying the fuel gas includes a
fuel-gas-flow regulator 417 for adjusting the total supply flow of the
fuel gas to be supplied to the fuel-gas-spraying nozzles 411a, 411c,
413a, and 413c, and on the other hand, the line for supplying the
oxygen-containing-gas includes an oxygen-containing-gas-flow regulator
418 for adjusting the total supply flow of the oxygen-containing-gas to
be supplied to the oxygen-containing-gas-spraying nozzles 411b, 411d,
413b, and 413d. The supply controller 420 adjusts the fuel-gas-flow
regulator 417 and the oxygen-containing-gas-flow regulator 418 so as to
control each entire flow of the fuel gas and the oxygen-containing-gas to
be supplied according to the combustion load. That is to say, in case of
small combustion load, the apertures of the fuel-gas-flow regulator 417
and the oxygen-containing-gas-flow regulator 418 are reduced so as to
reduce the total supply flow thereof. And on the other hand, in case of a
great combustion load, the apertures of the fuel-gas-flow regulator 417
and the oxygen-containing-gas-flow regulator 418 are increased so as to
increase the total supply flow thereof.

[0237]A fuel-gas flow-meter 421 and an oxygen-containing-gas flow-meter
422 measure each of total supply flow of the fuel gas and the
oxygen-containing-gas. And the measured values are sent to the supply
controller 420 so as to be used for adjusting the apertures of the
fuel-gas-flow regulator 417 and the oxygen-containing-gas-flow regulator
418.

[0238]Description will be made regarding a combustion control method for
the tubular flame burner using the combustion controller having such a
configuration with reference to FIG. 21 and FIG. 22.

[0239]In the method for controlling the combustion by the tubular flame
burner, the number of nozzles used for spraying the fuel gas and the
oxygen-containing-gas to the combustion chamber 410 is determined
according to the combustion load so that the fuel gas and the
oxygen-containing-gas are sprayed at an initial flow speed in a range
between the maximal permissive flow speed Vp dependent upon the pressure
loss and the minimal flow speed Vq required for forming a tube-shaped
flame.

[0240]That is to say, when increasing each total supply flow of the fuel
gas and the oxygen-containing-gas sprayed to the combustion chamber 410
according to the combustion load, in case that the switching valve 415a
opens while closing the other three switching valves 415c, 416a, and
416c, for spraying the fuel gas from only the fuel-gas-spraying nozzle
411a, and the switching valve 415b opens while closing the other three
switching valves 415d, 416b, and 416d, for spraying the
oxygen-containing-gas from only the oxygen-containing-gas-spraying nozzle
411b, all the supplied fuel gas flow is concentrated at the single
fuel-gas spraying nozzle 411a while concentrating all the supplied
oxygen-containing-gas flow at the single oxygen-containing-gas-spraying
nozzle 411b, and accordingly, the initial flow speed from the spraying
nozzles 411a and 411b is rapidly increased over the increased total
supply flow, i.e., increased combustion load, as shown by the line
L1 in FIG. 22A. As a result, while the flow speed rapidly reaches
the minimal flow speed Vq required for forming a tube-shaped flame, the
flow speed rapidly exceeds the maximal permissive flow speed Vp dependent
upon the pressure loss.

[0241]On the other hand, in case that the two switching valves 415a and
415c open while closing the other two switching valves 416a, and 416c,
for spraying the fuel gas from the two fuel-gas-spraying nozzles 411a and
411c, and in case that the switching valves 415b and 415d open while
closing the other two switching valves 416b and 416d, for spraying the
oxygen-containing-gas from the two oxygen-containing-gas-spraying nozzle
411b and 411d, the supplied fuel gas flow is divided into two halves so
as to be sprayed from the two fuel-gas spraying nozzles 411a and 411c,
respectively, and the supplied oxygen-containing-gas flow is divided into
two halves so as to be sprayed from the two oxygen-containing-gas
spraying nozzles 411b and 411d, respectively. Accordingly, the initial
flow speed from the spraying nozzles relatively gently increase over the
increased total supply flow, i.e., increased combustion load, as shown by
the line L2 in FIG. 22A. Specifically, in this case, the flow speed
increases over the combustion load with a half ratio as compared with a
case of using a single nozzle 411a for spraying the fuel gas and a single
nozzle 411b for spraying the oxygen-containing-gas. As a result, while
the flow speed relatively slowly reaches the minimal flow speed Vq
required for forming a tube-shaped flame, the flow speed relatively
slowly exceeds the maximal permissive flow speed Vp dependent upon the
pressure loss.

[0242]Furthermore, in a case that all the four switching valves 415a,
415c, 416a, and 416c, open for spraying the fuel gas from the four
fuel-gas-spraying nozzles 411a, 411c, 413a, and 413c, while opening all
the four switching valves 415b, 415d, 416b, ad 416d, for spraying the
oxygen-containing-gas from the four oxygen-containing-gas-spraying nozzle
411b, 411d, 413b, and 413d, the supplied fuel gas flow is divided into
four quarters so as to be sprayed from the four fuel-gas spraying nozzles
411a, 411c, 413a, and 413c, respectively, and the supplied
oxygen-containing-gas flow is divided into four quarters so as to be
sprayed from the four oxygen-containing-gas spraying nozzles 411b, 411d,
413b, and 413d, respectively. Accordingly, the initial flow speed from
the spraying nozzles extremely gently increases over the increased total
supply flow, i.e., the increased combustion load as shown by the line
L3 in FIG. 17A. Specifically, in this case, the flow speed increases
over the combustion load with a quarter ratio as compared with a case of
using a single nozzle 411a for spraying the fuel gas and a single nozzle
411b for spraying the oxygen-containing-gas. As a result, while the flow
speed considerably slowly reaches the minimal flow speed Vq required for
forming a tube-shaped flame, the flow speed considerably slowly exceeds
the maximal permissive flow speed Vp dependent upon the pressure loss.

[0243]Based on the above-described relation, the present combustion
control method determines that the number of the nozzles to be used for
spraying the fuel gas and the oxygen-containing-gas is adjusted by the
supply controller 420, which controls on/off of the switching valves
415a, 415b, 415c, 415d, 416a, 416b, 416c, and 416d. Such a determination
is done, in order for the fuel gas and the oxygen-containing-gas to be
sprayed into the combustion chamber 410, at an initial flow speed within
a range of the maximal permissive flow speed Vp and the minimal flow
speed Vq. Here, Vp is dependent upon the pressure loss, and Vq is
required for forming a tube-shaped flame. Specifically, as shown in FIG.
22B, when a combustion load is fallen within a range from the
predetermined minimal combustion load to that of approximately 1/4 of the
predetermined maximum combustion load, a single nozzle for spraying the
fuel gas and a single nozzle for spraying the oxygen-containing-gas are
used. When a combustion load is fallen within a range from a
approximately 1/4 of the predetermined maximum combustion load to
approximately 1/2 of the predetermined maximum combustion load, two
nozzles for spraying the fuel gas and two nozzles for spraying the
oxygen-containing-gas are used. Furthermore, in case of a combustion load
in a range between a load of approximately 1/2 to the predetermined
maximal combustion load, four nozzles for spraying the fuel gas and four
nozzles for spraying the oxygen-containing-gas are used.

[0244]Thus, as shown by the line M in FIG. 22A, the initial flow speed
from the spraying nozzles is obtained within a range between the maximal
permissive flow speed Vp (Vp is dependent on the pressure loss), and the
minimal flow speed Vq (Vp is required for forming a tube-shaped flame).
Such a procedure results in suppressing excessive pressure loss, while
maintaining the high speed of the flow required for forming a tube-shaped
flame.

[0245]As described above, the tubular flame burner according to the
present embodiment includes two nozzles that set along the tube axis.
Each of these nozzles is formed of two fuel-gas-spraying nozzles and two
oxygen-containing-gas-spraying nozzles along a single circumference of
the tubular combustion chamber 410. These nozzles have such a
configuration that the nozzles to be used for combustion are selected
from the multiple fuel-gas spraying nozzles and the oxygen-containing-gas
spraying nozzles. These nozzles are used by appropriately controlling
on/off of the switching values, so as to exhibit a predetermined flow
speed, even in case of change in the total supply flow of the fuel gas
and the oxygen-containing-gas, corresponding to change in the combustion
load. This results in suppressing the pressure loss at the time of an
increase of the supply flow, as well as maintaining formation of a swirl
at the time of reduction of the supply flow.

[0246]Note that while description has been made in the present embodiment
regarding the tubular flame burner including two nozzle sets along the
tube axis, each of which are formed of two fuel-gas spraying nozzles and
two oxygen-containing-gas spraying nozzles along a single circumference
thereof, the tubular flame burner may include a suitable number of nozzle
sets along the tube axis, each of which are formed of a suitable number
of fuel-gas spraying nozzles and two oxygen-containing-gas spraying
nozzles along a single circumference thereof, as appropriate.

[0247]Furthermore, description has been made in the present embodiment
regarding another arrangement. That is, the fuel-gas-spraying nozzles and
the oxygen-containing-gas-spraying nozzles are disposed so that each
spraying direction is in a tangential direction of the inner
circumferential wall of the combustion chamber. The arrangement according
to the present invention is not restricted to the aforementioned
arrangement. It may be a case, any spraying direction is not in a
tangential direction of the inner circumferential wall of the combustion
chamber as long as a swirl of a mixture gas is formed within the
combustion chamber.

[0248]Furthermore, description has been made in the present embodiment
regarding another arrangement. It may be a case, that the slits serving
as the nozzles for the combustion chamber are disposed along the tube
axis. And each slit is connected to the corresponding flat fuel-gas
spraying nozzle or oxygen-containing spraying nozzle. An arrangement may
be made, wherein multiple small-sized openings serving as a nozzle
orifice for the combustion chamber are formed along the tube axis. And
each nozzle is connected to the corresponding array formed of the
small-sized openings for spraying the fuel gas or the
oxygen-containing-gas.

[0249]Furthermore, description has been made in the present embodiment
regarding another arrangement, wherein the fuel gas is sprayed, but
liquid fuel may be sprayed. It may be a case, liquid fuel which readily
evaporate under relatively low temperature, such as kerosene, gas oil,
alcohol, A-type heave oil, or the like, is suitably employed as the
liquid fuel.

[0250]Note that the tubular flame burner according to the present
embodiment may also be formed with a polygonal cross-sectional shape
rather than round.

Embodiment 5-2

[0251]The present embodiment is shown in FIG. 26. FIG. 26 is an overall
configuration diagram, which shows a combustion controller for a tubular
flame burner according to the present embodiment.

[0252]The combustion controller, according to the above-described
embodiment 5-1, has such a configuration as the total flow of the fuel
gas and the total flow of the oxygen-containing-gas. Here, they are
supplied to the nozzles at the mounting portion A and/or the nozzles at
the mounting portion B are adjusted, as shown in FIG. 21. The combustion
controller according to the present embodiment has a configuration
wherein the fuel-gas flow and the oxygen-containing-gas flow to be
supplied to the nozzles mounted on the mounting portion A are
independently adjusted.

[0253]That is to say, as shown in FIG. 26, the line for supplying the fuel
gas to the nozzles at the mounting portion A includes a fuel-gas-flow
regulator 417a for controlling the fuel-gas flow to be supplied to the
fuel-gas spraying nozzles 411a and 411c. On the other hand, the line for
supplying the oxygen-containing-gas to the nozzles at the mounting
portion A includes an oxygen-containing-gas-flow regulator 418a for
controlling the oxygen-containing-gas flow to be supplied to the
oxygen-containing-gas spraying nozzles 411b and 411d. The fuel-gas-flow
regulator 417a and the oxygen-containing-gas-flow regulator 418a are
controlled by the supply controller, thereby enabling the fuel gas flow
and the oxygen-containing-gas flow to be adjusted in order to be supplied
to the nozzles at the mounting portion A. The flow-meter 421a for the
fuel gas and the flow-meter 422a for the oxygen-containing-gas measure
the supply amounts of the fuel gas and the oxygen-containing-gas,
respectively. And the measured values are sent to the supply controller
420a so as to be used for adjusting the apertures of the fuel-gas-flow
regulator 417a and the oxygen-containing-gas-flow regulator 418a. In the
same way, the line for supplying the fuel gas to the nozzles at the
mounting portion B includes a fuel-gas-flow regulator 417b for
controlling the fuel-gas flow to be supplied to the fuel-gas spraying
nozzles 413a and 413c. On the other hand, the line for supplying the
oxygen-containing-gas to the nozzles at the mounting portion B includes
an oxygen-containing-gas-flow regulator 418b for controlling the
oxygen-containing-gas flow to be supplied to the oxygen-containing-gas
spraying nozzles 413b and 413d. The supply controller 420b controls the
fuel-gas-flow regulator 417b and the oxygen-containing-gas-flow regulator
418b. The supply amounts of the fuel gas and the oxygen-containing-gas to
be supplied to the nozzles at the mounting portion B are measured by the
flow-meter 421b for the fuel gas, and the flow-meter 422b for the
oxygen-containing-gas, respectively. The measured values are sent to the
supply controller 420b so as to be used for adjusting the apertures of
the fuel-gas-flow regulator 417b and the oxygen-containing-gas-flow
regulator 418b.

[0254]The supply controller 420a for the nozzles at the mounting portion A
and the supply controller 420b for the nozzles at the mounting portion B,
are interconnected each other for adjusting the total supply flow of the
fuel gas and the oxygen-containing-gas.

[0255]Furthermore, switching valves 415a and 415c are provided for
controlling on/off of the supply of the fuel gas to the fuel-gas spraying
nozzles 411a and 411c at the mounting portion A. On the other hand, the
line for supplying the oxygen-containing-gas to the oxygen-containing-gas
spraying nozzles 411b and 411d at the mounting portion A includes
switching valves 415b and 415d for controlling on/off of supply of the
oxygen-containing-gas to the nozzles 411b and 411d, respectively. Here,
each of the switching valves 415a, 415b, 415c, and 415d, are controlled
by the supply controller 420a.

[0256]On the other hand, the aforementioned line for supplying the fuel
gas to the fuel-gas spraying nozzles 413a and 413c at the mounting
portion B includes switching valves 416a and 416c for controlling on/off
of the supply of the fuel gas to the fuel-gas-spraying nozzles 413a and
413c. On the other hand, the line for supplying the oxygen-containing-gas
to the oxygen-containing-gas spraying nozzles 413b and 413d at the
mounting portion B includes switching valves 416b and 416d for
controlling on/off of supply of the oxygen-containing-gas to the nozzles
413b and 413d. Here, each of the switching valves 416a, 416b, 416c, and
416d, are controlled by the supply controller 420b.

[0257]Thus, the supply controllers 420a and 420b control on/off of the
nozzles, thereby selecting the nozzles to be used for spraying the fuel
gas and the oxygen-containing-gas to the combustion chamber 410.

[0258]Thus, in the tubular flame burner according to the present
embodiment, the number of the nozzles to be used for combustion is
suitably selected from the multiple combustion-gas spraying nozzles and
oxygen-containing-gas spraying nozzles. Controlling on/off of the
switching valves does such a way, and this way is as well as adjusting
the flow supplied to each nozzle by controlling the corresponding
regulator, so as to obtain a predetermined spraying speed. It ends up in
suppressing the pressure loss when the supply flow increases, as well as
maintaining formation of a swirl when the supply flow reduces. Even in
the event of change in the total supply flow of the fuel gas and the
oxygen-containing-gas corresponding to change in the combustion load, the
above-mentioned procedure is done.

[0259]Note that the tubular flame burner according to the present
embodiment may also be formed with a polygonal cross-sectional shape
rather than round.

Embodiment 5-3

[0260]FIG. 23 through FIG. 25 show an embodiment 5-3 according to the
present invention. FIG. 23 is a side view of a tubular flame burner
according to the present embodiment, FIG. 24A is a cross-sectional view
taken along line A-A in FIG. 23, and FIG. 24B is a cross-sectional view
taken along line B-B in FIG. 23. FIG. 25 is an overall configuration
diagram, which shows a combustion controller for the tubular flame burner
according to the present embodiment.

[0261]In FIG. 23, reference numeral 410 is a tubular combustion chamber,
wherein the one end 410a opens so as to serve as an exhaust vent for
combustion exhaust gas. Furthermore, the tubular combustion chamber 410
includes two nozzle-mounting portions A and B along the tube axis on the
side of the rear-end 410b thereof for spraying a fuel gas and an
oxygen-containing-gas to the combustion chamber 410.

[0262]At the nozzle-mounting portion A, two long and narrow slits 432
extending along the tube axis are formed along the circumferential wall
of the combustion chamber 410, so as to serve as nozzles for the
combustion chamber 410. And such slits are connected to nozzles 431a and
431b, formed flat, and long and narrow along the tube axis, respectively,
as shown in FIG. 23 and FIG. 24A. These nozzles 431a and 431b are
disposed so that each spraying direction thereof is in a tangential
direction of the inner circumferential wall of the combustion chamber 410
so as to form a swirl in a predetermined direction. Note that a premixed
gas wherein the fuel gas and the oxygen-containing-gas have been mixed
beforehand is supplied to the nozzles 431a and the nozzles 431b.

[0263]The premixed gas is sprayed in the tangential direction of the
circumferential wall of the combustion chamber 410 at a high speed from
the premixed-gas spraying nozzles 431a and 431b to which the premixed gas
is supplied. This is done so as to form a swirl at a region near the
inner circumferential wall of the combustion chamber 410. When the
premixed gas forming such a swirl by an ignition device (not shown) such
as an ignition plug, pilot burner, or the like, are ignited, a
tube-shaped flame is formed within the combustion chamber 410.

[0264]In the same way, at the nozzle-mounting portion B, two long and
narrow slits 434 extending along the tube axis are formed along the
circumferential wall of the combustion chamber 410, so as to serve as
nozzles for the combustion chamber 410. And such slits are connected to
nozzles 433a and 433b, formed flat, and long and narrow along the tube
axis, respectively, as shown in FIG. 23 and FIG. 24B. These nozzles 433a
and 433b are disposed so that each spraying direction thereof is in a
tangential direction of the inner circumferential wall of the combustion
chamber 410 so as to form a swirl in a predetermined direction. Note that
a premixed gas wherein the fuel gas and the oxygen-containing-gas have
been mixed beforehand is supplied to the nozzles 433a and the nozzles
433b.

[0265]The premixed gas is sprayed in the tangential direction of the
circumferential wall of the combustion chamber 410 at a high speed from
the premixed-gas spraying nozzles 433a and 433b to which the premixed gas
is supplied. This is done, so as to form a swirl at a region near the
inner circumferential wall of the combustion chamber 410. When the
premixed gas forming such a swirl by an ignition device (not shown) such
as an ignition plug, pilot burner, or the like are ignited, a tube-shaped
flame is formed within the combustion chamber 410.

[0266]As described above, the tubular flame burner according to the
present embodiment includes two nozzles that set along the tube axis.
Each of these nozzles are formed of two premixed-gas spraying nozzles
along a single circumference of the combustion chamber, i.e., the tubular
flame burner according to the present embodiment includes four
premixed-gas spraying nozzles.

[0267]Furthermore, as shown in FIG. 25, the lines for supplying the
premixed gas to the premixed-gas spraying nozzles 431a, 431b, 433a, and
433b, include switching valves 435a, 435b, 436a, and 436b, for
controlling on/off of the supply of the premixed gas to the nozzles 431a,
431b, 433a, and 433b, respectively. And the lines further include gas
mixers 437a, 437b, 438a, and 438b, for premixing the fuel gas and the
oxygen-containing-gas beforehand, respectively.

[0268]The supply controller 420, thereby enabling the nozzles to be
selectively used for spraying the premixed gas to the combustion chamber
410, performs on/off control of the switching valves 435a, 435b, 436a,
and 436b.

[0269]The line for supplying the fuel gas to the gas mixers 437a, 437b,
438a, and 438b, includes a fuel-gas-flow regulator 417 for adjusting the
total flow of the fuel gas to be supplied. On the other hand, the line
for supplying the oxygen-containing-gas to the gas mixers 437a, 437b,
438a, and 438b, includes an oxygen-containing-gas-flow regulator 418 for
adjusting the total flow of the oxygen-containing-gas to be supplied. The
fuel-gas-flow regulator 417 and the oxygen-containing-gas-flow regulator
418 are controlled by the supply controller 420 so as to adjust the total
flow of the fuel gas and the total flow of the oxygen-containing-gas,
which are to be supplied, corresponding to the combustion load. That is
to say, when a combustion load is small, the apertures of the
fuel-gas-flow regulator 417 and the oxygen-containing-gas-flow regulator
418 reduces, so as to reduce the total supply flow. On the other hand,
when a combustion load is great, the apertures of the fuel-gas-flow
regulator 417 and the oxygen-containing-gas-flow regulator 418 increase
so as to increase the total supply flow.

[0270]Note that the flow-meter 421 for the fuel gas and the flow-meter 422
for the oxygen-containing-gas measure each of the total supply flow of
the fuel gas and the oxygen-containing-gas. And the measurement results
are sent to the supply controller 420, so as to be used for adjusting the
apertures of the fuel-gas-flow regulator 417 and the
oxygen-containing-gas-flow regulator 418.

[0271]Combustion control with the combustion controller for a tubular
flame burner having such a configuration is performed in the same way as
with the above-described embodiment.

[0272]That is to say, the number of the nozzles to be used for spraying
the premixed gas is adjusted by the supply controller 420 controlling
on/off of the switching valves 435a, 435b, 436a, and 436b, corresponding
to the combustion load, so that the initial flow speed of the premixed
gas sprayed to the combustion chamber is maintained in a range between
the maximal permissive flow speed Vp dependent upon the pressure loss and
the minimal flow speed Vq required for forming a tube-shaped flame.

[0273]For example, when a combustion load is fallen within a range from
the predetermined minimal combustion load to a load of approximately 1/4,
a single nozzle for spraying the premixed gas is used. And when a
combustion load is fallen within a range from a load of approximately 1/4
to approximately 1/2 thereof, two nozzles for spraying the premixed gas
are used. Furthermore, when a combustion load is fallen within a range
from a load of approximately 1/2 to the predetermined maximal combustion
load, four nozzles for spraying the premixed gas are used.

[0274]Thus, the initial flow speed from the spraying nozzles is obtained
within a range between the maximal permissive flow speed Vp (dependent
upon the pressure loss) and the minimal flow speed Vq (required for
forming a tube-shaped flame), thereby suppressing excessive pressure loss
while maintaining the high speed of the flow required for forming a
tube-shaped flame.

[0275]As described above, the tubular flame burner according to the
present embodiment includes two nozzles that set along the tube axis.
Each of these nozzles is formed of two nozzles for spraying the premixed
gas, along a single circumference of the tubular combustion chamber 410.
And the tubular flame burner, wherein the number of the nozzles to be
used for combustion, is suitably selected from the multiple nozzles for
spraying the premixed gas, by controlling on/off of the switching valves
so as to exhibit a predetermined flow speed, even in a case of change in
the total supply flow of the premixed gas corresponding to change in the
combustion load, thereby suppressing the pressure loss at the time of an
increase of the supply flow, as well as maintaining formation of a swirl
at the time of reduction of the supply flow.

[0276]Note that description has been made in the present embodiment
regarding the tubular flame burner including two nozzles that sets along
the tube axis. Each of these nozzles is formed of two nozzles for
spraying the premixed gas along a single circumference thereof. The
tubular flame burner may include a suitable number of nozzle sets along
the tube axis, each of which are formed of a suitable number of nozzles
for spraying the premixed gas along a single circumference thereof, as
appropriate.

[0277]Furthermore, description has been made in the present embodiment
regarding the arrangement, wherein the nozzles for spraying the premixed
gas are disposed so that each spraying direction is in a tangential
direction of the inner circumferential wall of the combustion chamber. An
arrangement according to the present invention is not restricted to the
aforementioned arrangement. An arrangement may be made wherein any
spraying direction is not in a tangential direction of the inner
circumferential wall of the combustion chamber as long as a swirl of a
mixture gas is formed within the combustion chamber.

[0278]Furthermore, while description has been made in the present
embodiment regarding the arrangement, wherein the slits serving as the
nozzles for the combustion chamber are disposed along the tube axis, and
each slit is connected to the corresponding flat nozzle for spraying the
premixed gas. An arrangement may be made wherein multiple small-sized
openings are formed along the tube axis, and each nozzle is connected to
the corresponding array formed of the small-sized openings for spraying
the premixed gas.

[0279]Furthermore, in the present embodiment, a gas formed by preheating
liquid fuel may be employed as a fuel gas. Note that liquid fuel which
readily evaporate under relatively low temperature, such as kerosene, gas
oil, alcohol, A-type heave oil, or the like, is suitably employed as the
liquid fuel.

[0280]Note that the tubular flame burner according to the present
embodiment may also be formed with a polygonal cross-sectional shape
rather than round.

Embodiment 5-4

[0281]The present embodiment is shown in FIG. 27. FIG. 27 is an overall
configuration diagram, which shows a combustion controller for a tubular
flame burner according to the present embodiment.

[0282]The combustion controller according to the above-described
embodiment 5-3 has a configuration. Here, the total flow of the fuel gas
and the total flow of the oxygen-containing-gas, which are to be supplied
to the premixed-gas spraying nozzles at the mounting portion A and/or to
the fuel-gas spraying nozzles at the mounting portion B, are adjusted as
shown in FIG. 25. The combustion controller according to the present
embodiment has a configuration wherein the fuel-gas flow and the
oxygen-containing-gas flow, which are to be supplied to the premixed-gas
spraying nozzles at the mounting portion A, are independently adjusted.

[0283]That is to say, as shown in FIG. 26, the line for supplying the fuel
gas to the premixed spraying nozzles 431a and 431b at the mounting
portion A includes the fuel-gas flow regulator 417a for adjusting the
flow of the fuel-gas, which is to be supplied. On the other hand, the
line for supplying the oxygen-containing-gas to the premixed spraying
nozzles 431a and 431b at the mounting portion A includes the
oxygen-containing-gas-flow regulator 418a for adjusting the flow of the
oxygen-containing-gas, which is to be supplied. The fuel-gas-flow
regulator 417a and the oxygen-containing-gas-flow regulator 418a are
controlled by the supply controller 420a, thereby enabling the fuel-gas
flow and the oxygen-containing-gas flow to be adjusted, which are to be
supplied to the premixed-gas spraying nozzles 431a and 431b at the
mounting portion A. The supply flow of the fuel gas and the supply flow
of the oxygen-containing-gas are measured by the flow-meter 421a for the
fuel gas and the flow-meter 422a for the oxygen-containing-gas,
respectively. And the measured results are sent to the supply controller
420a, so as to be used for adjusting the apertures of the fuel-gas-flow
regulator 417a and the oxygen-containing-gas-flow regulator 418a.

[0284]In the same way, the line for supplying the fuel gas to the premixed
spraying nozzles 433a and 433b at the mounting portion B includes the
fuel-gas-flow regulator 417b for adjusting the flow of the fuel gas which
is to be supplied. On the other hand, the line for supplying the
oxygen-containing-gas to the premixed spraying nozzles 433a and 433b at
the mounting portion B includes the oxygen-containing-gas-flow regulator
418b for adjusting the flow of the oxygen-containing-gas, which is to be
supplied. The supply controller 420b controls the fuel-gas-flow regulator
417b and the oxygen-containing-gas-flow regulator 418b. Such a
controlling method makes it possible to adjust the fuel-gas flow and the
oxygen-containing-gas flow, which are to be supplied to the premixed-gas
spraying nozzles 433a and 433b at the mounting portion B, and the
flow-meter for the oxygen-containing-gas. The supply flow of the fuel gas
and the supply flow of the oxygen-containing-gas are measured by the
flow-meter 421b for the fuel gas and the flow-meter 422b for the
oxygen-containing-gas, respectively. And the measured results are sent to
the supply controller 420b so as to be used for adjusting the apertures
of the fuel-gas-flow regulator 417b and the oxygen-containing-gas-flow
regulator 418b.

[0285]The supply controller 420a for the premixed-gas spraying nozzles
431a and 431b at the mounting portion A, and the supply controller 420b
for the premixed-gas spraying nozzles 433a and 433b at the mounting
portion B, are interconnected each other for adjusting the total supply
flow of the fuel gas and the oxygen-containing-gas.

[0286]Note that the line for supplying the premixed gas to the
premixed-gas spraying nozzle 431a at the mounting portion A from the gas
mixer 437a includes the switching valve 435a for controlling on/off of
supply of the premixed gas to the premixed-gas spraying nozzle 431a. And
the line for supplying the premixed gas to the premixed-gas spraying
nozzle 431b at the mounting portion A from the gas mixer 437b includes
the switching valve 435b for controlling on/off of supply of the premixed
gas to the premixed-gas spraying nozzle 431b.

[0287]On the other hand, the line for supplying the premixed gas to the
premixed-gas spraying nozzle 433a at the mounting portion B from the gas
mixer 438a includes the switching valve 436a for controlling on/off of
supply of the premixed gas to the premixed-gas spraying nozzle 433a. And
the line for supplying the premixed gas to the premixed-gas spraying
nozzle 433b at the mounting portion B from the gas mixer 438b includes
the switching valve 436b for controlling on/off of supply of the premixed
gas to the premixed-gas spraying nozzle 433b.

[0288]On/off control of the switching valves 435a and 435b is performed by
the supply controller 420a. And on/off control of the switching valves
436a and 436b is performed by the supply controller 420b. The nozzles to
be used for spraying, the premixed gas to the combustion chamber 410 are
selected by the aforementioned on/off control.

[0289]Thus, in the present embodiment, the number of the nozzles to be
used for combustion is suitably selected from the multiple nozzles for
spraying the premixed gas, by controlling on/off of the switching valves.
And the flow supplied to each nozzle is adjusted by controlling the
corresponding flow regulator, so as to exhibit a predetermined flow
speed. This is done, even in a case of change in the total supply flow of
the premixed gas corresponding to change in the combustion load. This
makes it possible to suppress the pressure loss when an increase of the
supply flow increases, as well as maintaining formation of a swirl at the
time of reduction of the supply flow.

[0290]In the present embodiment, the number of the nozzles to be used for
spraying the fuel gas and the oxygen-containing-gas to the combustion
chamber, or the number of the nozzles to be used for spraying the
premixed gas formed of the fuel gas and the oxygen-containing-gas to the
combustion chamber, is suitably selected so as to exhibit a predetermined
spraying speed. This is done, even in case of change in the total supply
flow of the fuel and oxygen-containing-gas corresponding to change in the
combustion load, thereby achieving stable combustion in a wider range of
the combustion load.

[0291]Note that the tubular flame burner according to the present
embodiment may also be formed with a polygonal cross-sectional shape
rather than round.

Embodiment 6

[0292]FIG. 28 through FIG. 31 show an embodiment 6 according to the
present invention. FIG. 28 is a side view of a tubular flame burner
according to the present embodiment, FIG. 29A is a cross-sectional view
taken along line A-A in FIG. 28. FIG. 30 is an overall configuration
diagram which shows a combustion controller for the tubular flame burner
according to the present embodiment, and FIG. 31 is an explanatory
diagram for describing a combustion control method for the tubular flame
burner according to the present embodiment.

[0293]In FIG. 28, reference numeral 510 denotes a tubular combustion
chamber, wherein the front-end 510a opens so as to serve as an exhaust
vent for a combustion exhaust gas. Furthermore, the combustion chamber
510 includes nozzles for spraying a fuel gas to the combustion chamber
510, and nozzles for spraying an oxygen-containing-gas thereto, near the
rear-end 510 thereof.

[0294]As shown in FIG. 28 and FIG. 29, the combustion chamber 510 includes
four long and narrow slits 512 arrayed along a single tube circumference.
Each of these slits are formed long along the tube axis thereof, so as to
serve as nozzles for the combustion camber 510, which are connected to
nozzles 511a, 511b, 511c, and 511d, formed flat, long and narrow along
the tube axis thereof, respectively. These nozzles 511a, 511b, 511c, and
511d, are disposed so that each spraying direction is in a tangential
direction of the inner circumferential wall of the combustion chamber 510
so as to form a swirl in a predetermined direction. Of these four
nozzles, the nozzles 511a and 511c serve as fuel-gas spraying nozzles,
and the nozzles 511b and 511d serve as oxygen-containing-gas spraying
nozzles.

[0295]The fuel gas is sprayed in the tangential direction of the inner
circumferential wall of the combustion chamber 510 at a high speed from
the fuel-gas spraying nozzles 511a and 511c. And, the
oxygen-containing-gas is sprayed in the tangential direction of the inner
circumferential wall of the combustion chamber 510 at a high speed from
the oxygen-containing-gas spraying nozzles 511b and 511d, so as to form a
swirl while efficiently mixing the fuel gas and the oxygen-containing-gas
at a neighborhood region of the inner circumferential wall of the
combustion chamber 510. When the mixture gas forming a swirl the tubular
flame burner is ignited by an ignition device (not shown) such as an
ignition plug, pilot burner, or the like, a tube-shaped flame is formed
within the combustion chamber 510. A combustion gas therefrom is
discharged from the front-end 510a of the combustion chamber 510.

[0296]Note that the oxygen-containing-gas represents a gas for carrying
oxygen used for combustion such as air, oxygen, oxygen-enriched air,
exhaust mixture gas, or the like.

[0297]Furthermore, as shown in FIG. 29A and FIG. 29B, a slit aperture
adjusting ring 513 is disposed at a portion, where the slits 512 are
disposed, so as to be in contact with the inner wall of the combustion
chamber 510 for adjusting the apertures of the slits 512. The slit
aperture-adjusting ring 513 is formed in the shape of a tube with a small
thickness. The slit aperture includes four slots along the
circumferential direction corresponding to the four slits 512, wherein
the apertures of the four slits 512 are adjusted by rotating the slit
aperture adjusting ring 513 in the direction of the tube circumference.

[0298]Specifically, FIG. 29A shows the combustion chamber 510, wherein the
slots of the slit aperture adjusting ring 513 just matches with the
corresponding slits 512, so as to adjust the aperture of each slit 512 to
the maximum. FIG. 29B shows the combustion chamber 510, wherein the slit
aperture adjusting ring 513 is rotated by a certain angle from the state
shown in FIG. 29A, so that a part of each slit 512 is closed with the
slit aperture adjusting ring 513 so as to reduce the aperture of each
slit 512.

[0299]Furthermore, as shown in the overall configuration diagram in FIG.
30, with the combustion controller for the tubular flame burner according
to the present embodiment, the line for supplying the fuel gas includes
the fuel-gas-flow regulator 517 for adjusting the flow of the fuel gas to
be supplied to the fuel-gas spraying nozzles 511a and 511c, and the line
for supplying the oxygen-containing-gas includes the
oxygen-containing-gas-flow regulator 518 for adjusting the flow of the
oxygen-containing-gas to be supplied to the oxygen-containing-gas
spraying nozzles 511b and 511d. The supply controller 520, so as to
adjust the supply flow of the fuel gas and the oxygen-containing-gas
corresponding to the combustion load; controls the fuel-gas-flow
regulator 517 and the oxygen-containing-gas-flow regulator 518.
Specifically, in case of a small combustion load, the apertures of the
fuel-gas-flow regulator 517 and the oxygen-containing-gas-flow regulator
518 are reduced, so as to reduce the supply flow thereof. On the other
hand, in case of a great combustion load, the apertures of the
fuel-gas-flow regulator 517 and the oxygen-containing-gas-flow regulator
518 are increased so as to increase the supply flow thereof.

[0300]Note that the supply flow of the fuel gas and the supply flow of the
oxygen-containing-gas are measured by the flow-meter 521 for the fuel gas
and the flow-meter 522 for the oxygen-containing-gas, respectively. And
the measurement results are sent to the supply controller 520 so as to be
used for adjusting the apertures of the fuel-gas-flow regulator 517 and
the oxygen-containing-gas-flow regulator 518.

[0301]Furthermore, a motor 514 is provided for adjusting the angular
position of the slit aperture adjusting ring 513, is controlled by the
supply controller 520, and adjusts the apertures of the slits 512 by
controlling the angular position of the slit aperture adjusting ring 513.
Note that an actuator such as a hydraulic cylinder, an air cylinder, or
the like, may be employed instead of the motor 514.

[0302]Description will be made regarding a combustion control method for
the tubular flame burner having such a configuration with reference to
FIG. 30 and FIG. 31.

[0303]In the method for controlling the combustion by the tubular flame
burner, when the supply flow is variable and changes corresponding to the
combustion load, the apertures of the slits 512 are adjusted in the
following way. That is, the initial flow speed of the fuel gas and the
oxygen-containing-gas sprayed to the combustion chamber 510 is maintained
within a range from the maximal permissive flow speed Vp (dependent upon
the pressure loss) and the minimal flow speed Vq (required for forming a
tube-shaped flame).

[0304]Specifically, as shown by the line L1 in FIG. 31A, when the
apertures of the slits 512 reduces, the initial flow speed of the flow
from the spraying nozzles 511a through 511d exhibits a rapid increase
corresponding to the increased supply flow, i.e., the increased
combustion load. As a result, while the flow speed rapidly reaches the
minimal flow speed Vq (required for forming a tube-shaped flame), the
flow speed rapidly exceeds the maximal permissive flow speed Vp
(dependent upon the pressure loss).

[0305]On the other hand, when the apertures of the slits 512 somewhat
increases, the initial flow speed of the flow from the spraying nozzles
exhibits a relatively gentle increase thereof corresponding to the
increased supply flow, i.e., the increased combustion load, as shown by
the line L2 in FIG. 31A. As a result, while the flow speed
relatively slowly reaches the minimal flow speed Vq (required for forming
a tube-shaped flame), the flow speed relatively slowly exceeds the
maximal permissive flow speed Vp (dependent upon the pressure loss).

[0306]Furthermore, when the apertures of the slits 512 increases to the
maximum, the initial flow speed of the flow from the spraying nozzles
exhibits an extremely gentle increase thereof corresponding to the
increased supply flow, i.e., the increased combustion load, as shown by
the line L3 in FIG. 31A. As a result, while the flow speed considerably
slowly reaches the minimal flow speed Vq (required for forming a
tube-shaped flame), the flow speed considerably slowly exceeds the
maximal permissive flow speed Vp (dependent upon the pressure loss).

[0307]In the present combustion control method, the supply controller 520
controls the angular position of the slit aperture adjusting ring 513, so
as to adjust the apertures of the slits 512 such that the initial flow
speed of the fuel gas. And the oxygen-containing-gas sprayed to the
combustion chamber 510 is maintained in a range between the maximal
permissive flow speed Vp (dependent upon the pressure loss) and the
minimal flow speed (Vq required for forming a tube-shaped flame based
upon the above-described relation).

[0308]Specifically, as shown in FIG. 31B, in case of a combustion load in
a range between the predetermined minimal combustion load to
approximately 1/3 of the predetermined maximal combustion load, the
apertures of the slits 512 are reduced. In case of combustion load in a
range between approximately 1/3 of the predetermined maximal combustion
load to approximately 2/3 thereof, the apertures of the slits 512
somewhat increases. Furthermore, in case of a combustion load in a range
between approximately 2/3 of the predetermined maximal combustion load to
the predetermined maximal combustion load, the apertures of the slits 512
increases to the maximum, to perform combustion.

[0309]Thus, as shown by the line M1 in FIG. 31A, the initial flow speed
from the spraying nozzles is maintained within a range from the maximal
permissive flow speed Vp (dependent upon the pressure loss) and the
minimal flow speed (Vq required for forming a tube-shaped flame),
resulting in suppressing excessive pressure loss while maintaining the
high speed of the flow required for forming a tube-shaped flame.

[0310]Description has been made regarding the method for controlling the
combustion, wherein the apertures of the slits 512 are adjusted in a
step-wise way, corresponding to the combustion load. But it may be a
case, a combustion control is performed, wherein the apertures of the
slits 512 are continuously adjusted corresponding to the combustion load
as shown in FIG. 31B. In such a way, the initial flow speed from the
spraying nozzles is maintained within a range from the maximal permissive
flow speed Vp (dependent upon the pressure loss) to the minimal flow
speed Vq (required for forming a tube-shaped flame) while maintaining a
constant flow speed, as shown by the line M2 in FIG. 31A.

[0311]Note that while description has been made in the present embodiment
regarding the arrangement, wherein the fuel-gas spraying nozzles and the
oxygen-containing-gas spraying nozzles are disposed so that each spraying
direction is in a tangential direction of the inner circumferential wall
of the combustion chamber. The arrangement of the present invention is
not restricted to the aforementioned arrangement. Another arrangement may
be made, wherein any spraying direction is not in a tangential direction
of the inner circumferential wall of the combustion chamber as long as a
swirl of the gas is formed within the combustion chamber.

[0312]Furthermore, description has been made in the present embodiment
regarding the arrangement, wherein the slits serving as the nozzles for
the combustion chamber are disposed along the tube axis, may be a case,
that each slit is connected to the corresponding fuel-gas spraying nozzle
or oxygen-containing-gas spraying nozzle. In such a case, the nozzle has
been formed flat, an arrangement may be made wherein multiple small-sized
openings are formed along the tube axis, and each of the fuel-gas
spraying nozzles and the oxygen-containing-gas spraying nozzles are
connected to the corresponding array formed of the small-sized openings.

[0313]Furthermore, description has been made in the present embodiment
regarding the arrangement wherein the fuel gas is sprayed, another
arrangement may be made wherein liquid fuel is sprayed. Note that liquid
fuel which readily evaporate under relatively low temperature, such as
kerosene, gas oil, alcohol, A-type heave oil, or the like, is suitably
employed as the liquid fuel.

[0314]Furthermore, description has been made in the present embodiment
regarding the arrangement wherein the fuel gas and the
oxygen-containing-gas are separately sprayed, an arrangement may be made
wherein a mixture gas formed by premixing the fuel gas and the
oxygen-containing-gas is sprayed.

[0315]According to the present embodiment, the apertures of the nozzle
orifices are adjusted so as to exhibit a predetermined flow speed. This
is done, even in case of change in the supply flow of the fuel and the
oxygen-containing-gas corresponding to change in the combustion load,
thereby enabling stable combustion to be in a wider range of the
combustion load.

[0316]Note that the tubular flame burner according to the present
embodiment may also be formed, with a polygonal cross-sectional shape
rather than round one.